
> So, a lot of new to Flutter developers are facing problems understanding initState() and didChangeDependencies() method, Though Flutter has got it covered in official docs but newbie developers are finding it hard to understand them.

### initState()

> According to Flutter official docs,Called when this object is inserted into the tree.
> 
> The framework will call this method exactly once for each  [State](https://api.flutter.dev/flutter/widgets/State-class.html)  object it creates.
> 
> Override this method to perform initialization that depends on the location at which this object was inserted into the tree (i.e.,  [context](https://api.flutter.dev/flutter/widgets/State/context.html)) or on the widget used to configure this object (i.e.,  [widget](https://api.flutter.dev/flutter/widgets/State/widget.html)).
> 
> **EXPLAINATION:-**
> 
> Whenever we start making a widget i.e a class and start building the layers or tree of widgets using Build Context(), we can initialize any variable, call any function or method before building the widget tree i.e before building the widget anything inside initState() function will be called or initialized first and the widgets are built later. Let me explain using a simple example:

![](https://miro.medium.com/max/415/1*5MBySpj2bxAAcJ7GVygQIg.jpeg)

Use of initState()

> As you can see in the code above, before building the widget tree initState() is initialized and called where print statement is used to print ‘open’, you can use initState() to set values to any variable,list or even use it to call any function.

### didChangeDependencies()

> According to Flutter official docs,Called when a dependency of this  [State](https://api.flutter.dev/flutter/widgets/State-class.html)  object changes.
> 
> For example, if the previous call to  [build](https://api.flutter.dev/flutter/widgets/State/build.html)  referenced an  [InheritedWidget](https://api.flutter.dev/flutter/widgets/InheritedWidget-class.html)  that later changed, the framework would call this method to notify this object about the change.
> 
> This method is also called immediately after  [initState](https://api.flutter.dev/flutter/widgets/State/initState.html). It is safe to call  [BuildContext.dependOnInheritedWidgetOfExactType](https://api.flutter.dev/flutter/widgets/BuildContext/dependOnInheritedWidgetOfExactType.html)  from this method.
> 
> Subclasses rarely override this method because the framework always calls  [build](https://api.flutter.dev/flutter/widgets/State/build.html)  after a dependency changes. Some subclasses do override this method because they need to do some expensive work (e.g., network fetches) when their dependencies change, and that work would be too expensive to do for every build.

**_EXPLAINATION:-_**

> Called when a dependency of this State object changes.
> 
> For example, if the previous call to build referenced an InheritedWidget that later changed, the framework would call this method to notify this object about the change.
> 
> This method is also called immediately after initState. It is safe to call BuildContext.dependOnInheritedWidgetOfExactType from this method.
> 
> its called before build after an InheritedWidget notifies you that it updated
> 
> its useful because it gives you an opportunity to compare and set state outside of build.
> 
> Lets take an example:
> 
> Theme.of(context) for example is glue for dependOnInheritedWidgetOfExactType,when that InheritedWidget updates e.g. from the theme changing, it will rebuild your widget.

## Why is it useful?

> its useful because it gives you an opportunity to compare and set state outside of build.
```
void didChangeDependencies() {
final greatplaces= Provider.of<GreatPlaces>(context); if(this.greatPlaces!=greatplaces)
{ 
this.greatPlaces=greatplaces;
getList= greatplaces.fetchAndSetPlaces();
}
super.didChangeDependencies();

}
```

![enter image description here](https://i.postimg.cc/MpjhS1hr/carbon.png)

> a possible condition for didChangeDependencies in the above snippet to be called here would be that your GreatPlaces provider updated.

*Hope you guys understood the difference between the two and you can play around with both the methods to get a hang of it. Have a good day you guys and see you all in the next article!*

initState and didChangeDependencies methods in Flutter Explained | Flutter Tips and Tricks

Sorting Algorithms Analyzer/Visualizer using Flutter | Best Flutter Project for Students | Flutter Developers

### Dog Breed Identification App with Flutter and tflite in 10 mins.


So,Today we are going to build an app that on given an image of a dog shows you what the breed of the dog is.For this I have used Google Teachable machine to train our classifying model and Flutter to get it working.

> **Let’s train our model first.**

-   Open Google Teachable machine in your Browser by clicking [here](https://teachablemachine.withgoogle.com/).


-   Now Click on ‘Get Started’ and then select Image Project.

![](https://miro.medium.com/max/700/1*yz_9Bfj2Ccpfwz2RHCkCMg.png)

-   Now,In the opened window there will be different classes you can use to train a modern on different labels.Here each class defines one dog breed.We will be training this model for 20 breeds so 20 classes will be trained.

![](https://miro.medium.com/max/700/1*UFRNKrBfBSGLkTZhV27H3A.png)

-   Now it’s time to get the data set. I have used a data this data set from kaggle.

[](https://www.kaggle.com/jessicali9530/stanford-dogs-dataset)
**[Stanford Dogs Dataset](https://www.kaggle.com/jessicali9530/stanford-dogs-dataset)**
Over 20,000 images of 120 dog breeds


-   In this dataset,there will be 120 folders containing 120 breeds.
-   Now, name every class with the name of the breed and insert that breed’s images using the upload option.

![](https://miro.medium.com/max/700/1*I6A8n4wckxd4z3hGwVSH_g.png)

-   After defining and uploading for 20 different breeds, Click on  **Train Model** which may take a while.
-   After your model is trained,you need to download that model. To download the model,Click on export model and then download the Floating point model under the  **Tensorflow Lite**  Window.

![](https://miro.medium.com/max/700/1*79somQonaG3dAmTCOn2bOg.png)

-   After downloading the model you will get 2 files, one is labels.txt and another is the model.

**So,The ML part is done now.Let’s get to flutter now.**

-   install tflite and image_picker packages in your flutter project.


**[tflite | Flutter Package](https://pub.dev/packages/tflite)**
 [**image_picker | Flutter Package**](https://pub.dev/packages/image_picker)

-   Now go to  **android/app/build.gradle**  and add this snippet inside android block.

```
aaptOptions{          
noCompress 'tflite'          
noCompress 'lite'      
}
```

-   Now create a assets folder in your project put both the model files in the assets folder i.e labels.txt and the model file.
-   Now open  **pubspec.yaml**  and update the assets parameter like this

```
assets:      
  - assets/
  
 ```

-   So,the configuration part is done now.Let’s code it now.

-   Let’s load the model first

```
void initState() {

  super.initState();
  _loading = true;
  loadModel().then((value) {
  setState(() {
     _loading = false;
  });
});
}

loadModel() async {
   await Tflite.loadModel(
      model: "assets/model_unquant.tflite",
      labels: "assets/labels.txt",
   );
}
```

![enter image description here](https://i.postimg.cc/QM5HLgf0/carbon-3.png)

-   After loading the model,setup picking image and classifying image function.

```
 pickImage() async {
    var image = await ImagePicker.pickImage(source: ImageSource.gallery);
    if (image == null) return null;
    setState(() {
      _loading = true;
      
      _image = image;
    });
    classifyImage(image);
  }

  // Classifiy the image selected
  classifyImage(File image) async {
    var output = await Tflite.runModelOnImage(
      path: image.path,
      numResults: 2,
      threshold: 0.5,
      imageMean: 127.5,
      imageStd: 127.5,
    );
    setState(() {
      _loading = false;
      //Declare List _outputs in the class which will be used to show the classified classs name and confidence
      _outputs = output;
    });
  }
  ```

![enter image description here](https://i.postimg.cc/CxwgMGMc/carbon.png)
-   That’s it and now just set a button that can let you pick an image and show it’s breed.

```
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:tflite/tflite.dart';
import 'package:image_picker/image_picker.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
       
        primarySwatch: Colors.blue,
        
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool
      _loading; 

  void initState() {
    super.initState();
    _loading = true;

    loadModel().then((value) {
      setState(() {
        _loading = false;
      });
    });
  }


  loadModel() async {
    await Tflite.loadModel(
      model: "assets/model_unquant.tflite",
      labels: "assets/labels.txt",
    );
  }

  File _image;
  List _outputs;
  pickImage() async {
    var image = await ImagePicker.pickImage(source: ImageSource.gallery);
    if (image == null) return null;
    setState(() {
      _loading = true;
      
      _image = image;
    });
    classifyImage(image);
  }

  // Classifiy the image selected
  classifyImage(File image) async {
    var output = await Tflite.runModelOnImage(
      path: image.path,
      numResults: 2,
      threshold: 0.5,
      imageMean: 127.5,
      imageStd: 127.5,
    );
    setState(() {
      _loading = false;
      //Declare List _outputs in the class which will be used to show the classified classs name and confidence
      _outputs = output;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Dog Breed Classifier'),backgroundColor: Colors.purple,),
      body: _loading
          ? Container(
              alignment: Alignment.center,
              child: CircularProgressIndicator(),
            )
          : Container(
              width: MediaQuery.of(context).size.width,
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  _image == null ? Container() : Image.file(_image),
                  SizedBox(
                    height: 20,
                  ),
                  _outputs != null
                      ? Text(
                          "${_outputs[0]["label"]}".replaceAll(RegExp(r'[0-9]'), ''),
                          style: TextStyle(
                            color: Colors.black,
                            fontSize: 20.0,
                            background: Paint()..color = Colors.white,
                            fontWeight: FontWeight.bold
                          ),
                        )
                      : Text("Classification Waiting")
                ],
              ),
            ),
      floatingActionButton: FloatingActionButton(
        onPressed: pickImage,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}
```

See the raw snippet right **[here](https://gist.githubusercontent.com/Himanshuranjan30/053101aa5753b27a4dd73150c21f685f/raw/9fbeef893a396c832d299e56c4a3bc8b2243bd32/main.dart)**.

![](https://miro.medium.com/max/540/1*sH5PEOEEL22KuFq2hnQdUg.jpeg)

**Wasn’t that cool! Check out the full code here:**
[Github](https://github.com/Himanshuranjan30/dog-breed-IdentifierFlutter)


Realtime Dog Breed Detection using Flutter | Machine Learning With Flutter | TensorFlow and Flutter

#### Today we are going to talk about how easy it is to call someone directly from your flutter app so that it can be implemented in a real-time working application.

**For this implementation, you will need `url_launcher`  package:**
Click **[here](https://pub.dev/packages/url_launcher)** to know more about installing and using it in your app.

[](https://pub.dev/packages/url_launcher)


**Let’s code it now:**

-   Declare this string url at the top.

`String url= 'tel:+91224578781';`

- Replace the number with the number you want to call to.

-   Let’s define a function to make it work.

```
Future<void> callnow() async{  
if(await canLaunch(url))  
{  
   await launch(url);  
}else  
{  
   throw 'call not possible';  
}  
}
```

![enter image description here](https://i.postimg.cc/cLpfc4g0/carbon-2.png)

-   Now run this function on a button press and you’ll be up and calling.

## That’s it for this article,See you guys in the next one.

Make a Phone Call using Flutter App | Easy Flutter Tutorials

#### So, Today we are gonna talk about and understand how we can import images from ‘ON-DEVICE STORAGE’ or ‘CAMERA’ to our flutter apps and store it in device storage too.

#### There are 3 Dart packages you’ll need to implement this:


- [**path_provider | Flutter Package**](https://pub.dev/packages/path_provider)

- **[Path Package](https://pub.dev/packages/path/install)**

- [**image_Picker**](https://pub.flutter-io.cn/packages/image_picker)




## Implementation:

> Lets make a function to use this image_picker feature.
```
File _storedImage;Future<void> _takePicture() async {      
final imageFile = await ImagePicker.pickImage(source: ImageSource.camera,        
maxWidth: 600,      
);      
if (imageFile == null) {        
return;     
}      
setState(() {        
_storedImage = imageFile;      
});      
final appDir = await syspaths.getApplicationDocumentsDirectory();    final fileName = path.basename(imageFile.path);      
final savedImage = await imageFile.copy('${appDir.path}/$fileName');    }
```
## Explanation:

-   As we know image is type of File so we create a File type variable to store image in it.
-   Create a function with a Future return type as accessing a image from gallery or camera takes a bit of time.
-   Now store the image that you picked from gallery or camera in a imageFile variable.

```
//From camera  
final imageFile = await ImagePicker.pickImage(source: ImageSource.camera)//From Gallery  
final imageFile = await ImagePicker.pickImage(source: ImageSource.gallery)

-   Now check  whether the image file is picked  or not.

if (imageFile == null) {        
return;     
}
```
-   Now store the picked image file in _StoredImage variable.

```
setState(() {        
_storedImage = imageFile;      
});
```
-   Get access to local storage using path provider package, here we access the app’s directory that gets created everytime we install an app and use that directory to store app files, Here we will store all our app images.
```
final appDir = await syspaths.getApplicationDocumentsDirectory();
```
-   Now we have to fetch name of the image that we have fetched to store it in the storage with the same name and that’s where path package comes handy, basename gets the name of the image in the last seperator like: folder/images/testimage.jpg , So, basename will gets the string ‘testimage.jpg’ as the name of the image.
```
\\Gets the part of path after the last separator.  
final fileName = path.basename(imageFile.path);
```
-   Now we save the image in our app’s directory using app directory name and image name and final image gets saved in a variable savedImage too.

```
final savedImage = await imageFile.copy('${appDir.path}/$fileName');
```
#### So, That’s it for this section. You have successfully fetched an image from gallery or camera and stored it in your app directory for furthur use. see you guys in the next article. Cheers!

Using Image Picker with Flutter and storing images in Local Storage | Quick Flutter Guide | Mobile App Development

Today we are going to talk about what really riverpod is and how you can develop production ready complex apps with this powerful state management technique.

[Check out the riverpod package here](https://pub.dev/packages/flutter_riverpod)

So,Riverpod is basically provider boosted to an another level with ease of functionalities.

> **Features of Riverpod that makes it very special:**

-   **Declare** **State from anywhere**

No need to jump between your  `main.dart`  and your UI files anymore.

Place the code of your shared state where it belongs, be it in a separate package or right next to the Widget that needs it, without losing testability.

-   **Recompute states/rebuild UI only when needed**

We no-longer have to sort/filter lists inside the  `build`method or have to resort to advanced cache mechanism.

With`[Provider](https://riverpod.dev/docs/concepts/combining_providers)`and["families"](https://riverpod.dev/docs/concepts/modifiers/family), sort your lists or do HTTP requests only when you truly need it.

-   **Safety Read Providers**

Reading a provider will never result in a bad state. If you can write the code needed to read a provider, you will obtain a valid value.

This even applies to asynchronously loaded values. As opposed to with provider, Riverpod allows cleanly handling loading/error cases.

> **To Understand it a bit more let’s make a Notes App of our own:**

-   In order to access riverpod or the state features through out our whole app,we need to wrap the parent widget with  `ProviderScope`  wrapper.

```
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:noteapp/dashboard.dart';

void main() {
runApp(MyApp());
}

class MyApp extends StatelessWidget {

// This widget is the root of your application.

@override
Widget build(BuildContext context) {

return ProviderScope(

  child: MaterialApp(
  title: 'Flutter Demo',
  theme: ThemeData(
  visualDensity: VisualDensity.adaptivePlatformDensity,

),

home: DashBoard(),
  routes: {
     "/dashboard": (context) => DashBoard(),
},
),
);
}

}
```
![enter image description here](https://i.postimg.cc/L8qTCYpZ/carbon-httpsn4.png)

-   After we wrap our app with the  `ProviderScope`  , we will be able to access and manage states from anywhere in our app.
-   Let’s make our  `Notifier`class now which will help us manage the state and data throughout our app.

```
import 'package:flutter/widgets.dart';

class Notifier extends ChangeNotifier {
    List Notes = ["First"];
    void onsubmit(String a) {
     Notes.add(a);
     notifyListeners();
}
}
```

![enter image description here](https://i.postimg.cc/PJwXVQ2R/carbon.png)

-   Here, we created a notifier class named Notifier(any name you like) that extends ChangeNotifier that will help us store and append different strings in our Notes List.
-   We created a List with 1 item and created a function named  `onsubmit`  that will add a string to the list and notify our whole app that a string has been added to the Notes List.
-   Let’s create our dashboard screen now that will show all the notes that you will add in your app.

```
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/all.dart';
import 'package:noteapp/notifier.dart';

final notesprovider = ChangeNotifierProvider<Notifier>((ref) {
  return Notifier();
});

class NotesList extends ConsumerWidget {

@override
Widget build(BuildContext context, ScopedReader watch) {

final noteswatcher = watch(notesprovider);
return Expanded(

  child: ListView.builder(
     itemBuilder: (context, int index) {
     print(noteswatcher.Notes[index]);

return Text(noteswatcher.Notes[index]);

},

itemCount: noteswatcher.Notes.length,

),
);
}
}

class DashBoard extends StatelessWidget {

@override
Widget build(BuildContext context) {

final notes = TextEditingController();
return Scaffold(
   appBar: AppBar(),
   body: Column(
   children: [
      TextField(
       controller: notes,
   ),

FlatButton(
   onPressed: () => context.read(notesprovider).onsubmit(notes.text),
   child: Text('Submit')),
NotesList(),
],
),
);
}
}

```

![enter image description here](https://i.postimg.cc/mZCPk4GM/carbon-1.png)

-   So,we are creating a TextField which will take a string input to add to the Notes.

-   The widget that is changing its state on every button press is  `ListView`  so, NotesList class which is returning a ListView extends a  `ConsumerWidget`  as the change is only happening in the List and Consumer will access all the changes given by the provider.
-   The fun thing about provider is that we don’t need a context to access our changenotifier and can be used pretty easily. As we can see that we are accessing our changenotifier globally which is later used in the below code.
-   `watch`  method is used to watch all the changes that are happening with the Notes List.
-   `read`  method is used to read a provider without listening to it.

The app is fully built now:

![](https://miro.medium.com/max/700/1*LdDH9dffud5PChKgXAiwrg.png)

As you can see that on every button press we are able to add notes to the List and render them on the dashboard.

Get the complete github source code from **[here](https://github.com/Himanshuranjan30/NotesApp_riverpod)**.

That's it for today and see you guys in the next one!

Flutter Riverpod ft. Notes app in 10 minutes | Flutter State Management made easy

## Today we are going to talk about how we can integrate flutter with a node.js and MongoDB backend to store images on the server with the help of popular node.js package “Multer”.

> What really is Multer?

Multer is a node.js middleware for handling  `multipart/form-data`, which is primarily used for uploading files. It is written on top of  [busboy](https://github.com/mscdex/busboy)  for maximum efficiency.You can read the documentation **[here](https://www.npmjs.com/package/multer)**:


## multer

### Multer is a node.js middleware for handling multipart/form-data, which is primarily used for uploading files. It is…

www.npmjs.com

In this session,we are going to make a simple flutter app to pick image from the phone’s gallery and send it over the server and save it for later use using multer and MongoDB.

Let’s get started.

-   First of all make a node.js folder using  `npm init`  and make a server.js file.
-   Let’s install the npm packages that we need for this project using the given command:

npm install express mongoose nodemon multer

-   Import all the packages in your server file.

```
const express= require('express')  
const multer=require('multer')  
const path= require('path')  
const app= express();  
const mongoose= require('mongoose')  
const model = require('./model')app.get('/',(req, res) => {      
res.send('We are at home')    
});
```

-   Configure your multer storage parameters that includes which folder you would like to set for saving the incoming images and the name of the images to be set.

```
var storage = multer.diskStorage({      
destination: function (req, file, cb) {        
cb(null, 'uploads')      
},   
     
filename: function (req, file, cb) {        
cb(null, new Date().toISOString()+file.originalname  
)      
}    
})

```
-   Let’s set up our routes now to serve the incoming requests.

```
app.post('/upload', upload.single('myFile'), async(req, res, next) => { const file = req.file      
if (!file) {        
const error = new Error('Please upload a file')      error.httpStatusCode = 400        
return next("hey error")      
}                    
const imagepost= new model({          
image: file.path        
})  
        
const savedimage= await imagepost.save()        
res.json(savedimage)        
}) app.get('/image',async(req, res)=>{     
const image = await model.find()     
res.json(image)       
})

```
-   After setting up the routes,let’s connect our server to mongoDB using mongoose package.

```
mongoose.connect(YOUR_MONGODB_URL,{ useNewUrlParser: true },()=>{  console.log('db connnected')})app.listen(3000);
```
-   We will be creating the collection model now which is already been used in the routes.
-   Here’s the complete server.js code:

```
const express= require('express')
const multer=require('multer')
const path= require('path')
const models= require('./model')
const app= express();
const mongoose= require('mongoose');
const model = require('./model');

app.get('/',(req, res) => {
res.send('We are at home')
});

app.use('/uploads', express.static(__dirname +'/uploads'));

var storage = multer.diskStorage({
  destination: function (req, file, cb) {
      cb(null, 'uploads')
},

filename: function (req, file, cb) {
cb(null, new Date().toISOString()+file.originalname)
}
})

var upload = multer({ storage: storage })

app.post('/upload', upload.single('myFile'), async(req, res, next) => {

const file = req.file
if (!file) {
  const error = new Error('Please upload a file')
  error.httpStatusCode = 400

  return next("hey error")
}

const imagepost= new model({
image: file.path
})

const savedimage= await imagepost.save()
res.json(savedimage)

})

app.get('/image',async(req, res)=>{
 const image = await model.find()
 res.json(image)

})

mongoose.connect("mongodb+srv://himu:himu@cluster0.qkmvt.mongodb.net/test?retryWrites=true&w=majority",{ useNewUrlParser: true },()=>{

console.log('db connnected')

})

app.listen(3000);
```

![enter image description here](https://i.postimg.cc/5tpVK1mQ/carbon-1.png)

-   Let’s create our model now that will help us upload image url’s in MongoDB.

```
const mongoose= require('mongoose');
const imageSchema= mongoose.Schema(
{

  image:{
    type: String,
    required: true
    }
}
);

module.exports=mongoose.model("Images",imageSchema)
```

-   Make sure you make your uploads(The folder where all the incoming images will be saved) folder which is in the same folder as that of your node folder is statically available to your server.js code using this:
```
app.use('/uploads', express.static(__dirname +'/uploads'));
```
-   We’re done with the backend part now,Let’s make our frontend using flutter.

```
import 'dart:convert';
import 'dart:ffi';
import 'dart:io';
import 'dart:async';
import 'package:async/async.dart';
import 'package:http/http.dart' as http;
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'package:path/path.dart';

class ImageUpload extends StatefulWidget {

@override
_ImageUploadState createState() => _ImageUploadState();

}

class _ImageUploadState extends State<ImageUpload> {

File _image;
final picker = ImagePicker();

Future<void> getImage() async {
final pickedFile = await picker.getImage(source: ImageSource.gallery);

setState(() {
 if (pickedFile != null) {
 _image = File(pickedFile.path);
} else {
  print('No image selected.');
}
});
}

upload(File imageFile) async {

// open a bytestream
var stream =
new http.ByteStream(DelegatingStream.typed(imageFile.openRead()));

// get file length
var length = await imageFile.length();

// string to uri
var uri = Uri.parse("http://192.168.0.8:3000/upload");

// create multipart request
var request = new http.MultipartRequest("POST", uri);

// multipart that takes file
var multipartFile = new http.MultipartFile('myFile', stream, length,

filename: basename(imageFile.path));

// add file to multipart
request.files.add(multipartFile);

// send
var response = await request.send();

print(response.statusCode);

// listen for response
response.stream.transform(utf8.decoder).listen((value) {

print(value);

});

}

bool isloaded = false;
var result;

fetch() async {
var response = await http.get('http://192.168.0.8:3000/image');
result = jsonDecode(response.body);
print(result[0]['image']);
setState(() {
isloaded = true;

});

}

@override
Widget build(BuildContext context) {
  fetch();
  return Scaffold(
     appBar: AppBar(),
     body: Column(

     children: [

      Text("Select an image"),
      FlatButton.icon(
          onPressed: () async => await getImage(),
          icon: Icon(Icons.upload_file),
          label: Text("Browse")),

      SizedBox(
         height: 20,
        ),

      FlatButton.icon(

        onPressed: () => upload(_image),
        icon: Icon(Icons.upload_rounded),
        label: Text("Upload now")),
        isloaded? Image.network('http://192.168.0.8:3000/${result[0]['image']}')
       : CircularProgressIndicator(),
],
),
);
}
}
```

Get the complete snippet from **[here](https://gist.githubusercontent.com/Himanshuranjan30/23df26d1f1764ef5d1abf94da0e93f70/raw/a7d08210b57487a26d1fecc1f8719fcc853d971e/Imageupload.dart)** or use *github* link below.

-   In the above code, we are picking up a image using image picker then reading the image as a bytes stream and later posting it to our node.js server using  `Multipart Form`  request.

> Note: Make sure your use the same image name that you used in your node.js server i.e  `myFile`  here.

-   After a succesfull post request you can see your image uploaded in  `uploads`  folder inside your node server folder.

![](https://miro.medium.com/max/1400/1*MxFianvrt7qZqPT91OaK-Q.png)

-   After successfull upload,we are saving the image path on to our  `MongoDB`  database in order to fetch that image later in your app.

![](https://miro.medium.com/max/1400/1*kANj20bUVnLLEi6QMS6Wog.png)

-   In order to fetch back all the image paths of all the images that got stored in the server,we are sending an http request which is collecting all the paths from mongodb and sending it back as a json file.
-   After getting the image path,we can use it in our flutter app as:

`Image.network("[http://localhost:3000/](http://localhost:3000/)IMAGE_PATH");//IMAGE_PATH: Path you got from MongoDB.`

-   That’s how you can use multer and MongoDB to store image on to your node.js server.

For Github Repo Click **[here](https://github.com/Himanshuranjan30/multer_nodejs_flutter)**.

Flutter File upload using Multer,Node.js and MongoDB | Flutter and Node.js Integration with MongoDB

In this article,we will be going through how we can integrate Google calendar with our Spring boot api and push and fetch events to yours or anyone else's calendar.

Let's start with setting up our client authentication details using the Google cloud console.

Here I have created a new project,Now go to the hamburger icon on top left then -> API and Services -> Enable API and Services -> Search `Google Calendar Api` and Enable it. After that under the same API and Services dashboard click on `credentials`.

In `credentials` screen,click on CREATE CREDENTIALS.

![](https://miro.medium.com/max/700/1*A4W8cR10MT8Rc0E7qwXGLA.png)

Click on Service Account and simply create one.Now after creating a service account you can see your created account in the above dashboard.Now click on your service account email then -> Keys -> Create New Key -> Select `p12` format and a `p12` file will be downloaded in yout system.

The console configuration part is done now.Its time to code now!!!

Now create a spring boot project with `spring-starter-web` dependency.Let's see our `pom.xml` file now and add few more dependencies.


```
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.4.4</version>
		<relativePath/> 
	</parent>
	<groupId>com.first</groupId>
	<artifactId>firstapp</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>firstapp</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>11</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
  <dependency>
    <groupId>com.google.apis</groupId>
    <artifactId>google-api-services-calendar</artifactId>
    <version>v3-rev411-1.25.0</version>
</dependency>

<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.2</version>
</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>
```

![enter image description here](https://i.postimg.cc/vmZGcNBY/issue-social-banner.png)


```
\
<dependency>\
    <groupId>com.google.apis</groupId>\
    <artifactId>google-api-services-calendar</artifactId>\
    <version>v3-rev411-1.25.0</version>\
</dependency>
```

Find this dependency here: <https://mvnrepository.com/artifact/com.google.apis/google-api-services-calendar>

Now let's get straight to writing a endpoint that will do the `fetch` and `push` events for us.

```
package com.first.firstapp.controllers;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.security.GeneralSecurityException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Arrays;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TimeZone;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.view.RedirectView;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.first.firstapp.entities.course;
import com.first.firstapp.services.courseservice;
import com.google.api.client.auth.oauth2.AuthorizationCodeRequestUrl;
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.auth.oauth2.TokenResponse;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets.Details;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.repackaged.com.google.common.base.Preconditions;
import com.google.api.client.repackaged.com.google.common.base.Strings;
import com.google.api.client.util.DateTime;
import com.google.api.services.calendar.CalendarScopes;
import com.google.api.services.calendar.Calendar.Events;
import com.google.api.services.calendar.model.Event;
import com.google.api.services.calendar.model.EventAttendee;
import com.google.api.services.calendar.model.EventDateTime;
import com.google.api.services.calendar.model.EventReminder;

@RestController
public class mycontroller {

private final static Log logger = LogFactory.getLog(mycontroller.class);
private static final String APPLICATION_NAME = "serviceCal";
private static HttpTransport httpTransport;
private static final JsonFactory JSON_FACTORY = new JacksonFactory();
private static com.google.api.services.calendar.Calendar client;
URL url = getClass().getResource("auth.p12");
File keyFile=new File(url.getPath());
GoogleClientSecrets clientSecrets;
GoogleAuthorizationCodeFlow flow;
Credential credential;
HttpTransport TRANSPORT ;

private String SERVICE_ACCOUNT="test-825@openforum-307505.iam.gserviceaccount.com";
private Set<Event> events = new HashSet<>();

public void setEvents(Set<Event> events) {
this.events = events;
}

@RequestMapping(value = "/add", method = RequestMethod.GET)
public ResponseEntity<String> oauth2Callback(HttpServletRequest request) throws IOException, GeneralSecurityException {

com.google.api.services.calendar.model.Events eventList;

String message;
// TokenResponse response = flow.newTokenRequest(code).setRedirectUri(redirectURI).execute();
// credential = flow.createAndStoreCredential(response, "userID"); //for Oauth2
Preconditions.checkArgument( !Strings.isNullOrEmpty(APPLICATION_NAME ),
"applicationName cannot be null or empty!" );

try {

TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();

credential = new GoogleCredential.Builder().setTransport(TRANSPORT)

.setJsonFactory(JSON_FACTORY)

.setServiceAccountId(SERVICE_ACCOUNT)

.setServiceAccountScopes(Collections.singleton(CalendarScopes.CALENDAR))

.setServiceAccountPrivateKeyFromP12File(keyFile)

.build();

credential.refreshToken();

client = new com.google.api.services.calendar.Calendar.Builder(TRANSPORT, JSON_FACTORY, credential)

.setApplicationName(APPLICATION_NAME).build();

System.out.println(client);

Events events = client.events();

eventList = events.list("primary").setTimeMin(date1).setTimeMax(date2).execute();

message = eventList.getItems().toString();

Event event = new Event()

.setSummary("Google I/O 2015")

.setLocation("800 Howard St., San Francisco, CA 94103")

.setDescription("A chance to hear more about Google's developer products.");

DateTime startDateTime = new DateTime("2021-07-31T09:00:00-07:00");

EventDateTime start = new EventDateTime()

.setDateTime(startDateTime)

.setTimeZone("America/Los_Angeles");

event.setStart(start);

DateTime endDateTime = new DateTime("2021-08-01T17:00:00-07:00");

EventDateTime end = new EventDateTime()

.setDateTime(endDateTime)

.setTimeZone("America/Los_Angeles");

event.setEnd(end);

String[] recurrence = new String[] {"RRULE:FREQ=DAILY;COUNT=2"};

event.setRecurrence(Arrays.asList(recurrence));

// EventAttendee[] attendees = new EventAttendee[] {

// new EventAttendee().setEmail("greatgatsbylala18@gmail.com"),

// new EventAttendee().setEmail("himanshuranjan3030@gmail.com"),

// };

// event.setAttendees(Arrays.asList(attendees));

EventReminder[] reminderOverrides = new EventReminder[] {

new EventReminder().setMethod("email").setMinutes(24 * 60),

new EventReminder().setMethod("popup").setMinutes(10),

};

Event.Reminders reminders = new Event.Reminders()

.setUseDefault(false)

.setOverrides(Arrays.asList(reminderOverrides));

event.setReminders(reminders);

String calendarId = "primary";

event = client.events().insert("putyouremailhere@gmail.com", event).execute();

System.out.printf("Event created: %s\n", event.getHtmlLink());

System.out.println("cal message:" + message);

return new ResponseEntity<>(message, HttpStatus.OK);

}catch(IOException e)

{

System.out.println(e);

}

return new ResponseEntity<>("Nothing", HttpStatus.OK);

}

public Set<Event> getEvents() throws IOException {

return this.events;

}

}
```

Find the complete snippet **[here](https://gist.githubusercontent.com/Himanshuranjan30/401b59ea14d429bbaf80072355cdd687/raw/191adfa5bc4ffc6b891e4dbc091c1cd1cf6e9b38/Controller.java)**.

Let's go through what we really did here...

-   I have saved the `p12` file that we downloaded from Google cloud console in the same project folder and I am using that file to set my client credentials which will be used for `fetching` and `pushing` the events to anyone's calendar.
-   Now I am using the client setup using the credentials in `auth.p12` file to fetch and push events.

BUT THERE'S 1 MORE THING THAT YOU NEED TO DO IN ORDER TO MAKE IT WORK.

We have to create a service google account of ourself,we can use our personal google accounts too but I wont recommend that for production level code.

Now this google account will act as a event organizer for creating any event in `Google Calendar`.Lets see what we have to do:

Go to your Google Calendar -> Click on your Calendar name -> Go to settings and Sharing -> Share with specific people and then:

![](https://miro.medium.com/max/700/1*9_ASHHalZleV5y_NRZC_eQ.png)

Add your service account email in the share with specific people field.Now you're the offical event organizer for any event you create for your friends calendar.Any event created with this service account will have you as a event organizer.

After doing this run your api,you will see an event added to the calendar of the email you put in this line:

event = client.events().insert("putyouremailhere@gmail.com", event).execute();

This email id must be same as that you used to access the calendar above and added the service account in the above picture. In this case:

`himanshuranjan30@gmail.com`

In order to add an event to anyone's calendar,we need to activate `Domain-Wide Delegation` .

IMPORTANT!!!
------------

In enterprise applications you may want to programmatically access users data without any manual authorization on their part. In Google Workspace domains, the domain administrator can grant to third party applications domain-wide access to its users' data --- this is referred as domain-wide delegation of authority. To delegate authority this way, domain administrators can use service accounts with OAuth 2.0.

Do comment on this article if you want an article on `Oauth`Implementation of Google Calendar API.

Thanks for tuning in,See you in the next one.PEACE OUT!

Google Calendar Integration with Spring Boot / Push and Fetch Events.

Hey devs

**SiteMaps** are one of the most important things when it comes to indexing your website in google search.
It can have a very major effect on your website traffic.
It basically generates **URLs** of all the pages your website has and put that in `sitemap.xml` file which Google tracks to index all those urls.
Today we're gonna see how we can generate dynamic sitemaps for our *Next.js* websites.

- Install `next-sitemap` which will help us create sitemaps for our pages dynamically.Read more about it [here](https://www.npmjs.com/package/next-sitemap).

- Now create a `next-sitemap.js` file in your root directory which will contain configuration for your sitemap file.

```
const siteUrl = "https://www.devdad.org";
module.exports = {
    siteUrl,
    generateRobotsTxt: true,
    robotsTxtOptions:{
    policies: [
    {
       userAgent: '*', allow: '/',
    }
    ]
    },
    additionalSitemap: [
       `${siteUrl}/server-sitemap.xml`,
       `${siteUrl}/sitemap.xml`,
    ],
 };
```

![enter image description here](https://i.postimg.cc/9z5qYYqg/carbon-sitemap2.png)

In the configuration,pass your siteUrl then tell your config to robots.txt is to be generated.
A **robots. txt** file tells search engine crawlers which URLs the crawler can access on your site.
It will contain the mapping to sitemap files that will be created later.

As robots.txt will contain sitemaps,its also good those sitemaps to *additionalSitemap* so that google can access them directly.

- We need to run this script post the build as it will generate sitemaps for all the pages,to run this script post build,add this in package.json:

```
"scripts": {
"dev": "next dev",
"build": "next build",
"start": "next start",
"lint": "next lint",
"postbuild": "next-sitemap"
},
```

`next build` will build this website and after the build,postbuild command will run which will further run the **next-sitemap** script.

This script will create 3 files under public folder i.e `robots.txt` , `sitemap.xml` and `sitemap-0.xml`.

*sitemap.xml* contains link to *sitemap-0.xml* which further contains url for all the components under pages folder i.e static pages.

As the static sitemaps are generated now,lets generate dynamic sitemaps now.

- For creating dynamic sitemaps,create a folder inside `pages` folder named  `server-sitemap.xml`  under which make a component `index.jsx` like this:
```

import { getServerSideSitemap } from  "next-sitemap";
export  async  function  getServerSideProps(context){
const  url  =  "https://www.devdad.org/Post";
const  response  =  await  fetch("https://API_URL/posts/");
const  posts  =  await  response.json();
console.log(posts);
const  fields=posts.map(post=>({

loc: `${url}?title=${post.title.replace(/[^A-Z0-9]/ig, '')}-${post._id}`,
lastmod:new  Date().toISOString()
}));
return  getServerSideSitemap(context,fields);
}
export  default  function  Site() {};
```

![enter image description here](https://i.postimg.cc/HxzFd3Qq/SITEMAP.png)

Now as you all know,devdad is a blog site and I need to index every single page in order to get traffic from all arountd the world.

In the above snippet,I fetching all my posts and and making the url for all the blogs and siteMapping it using **getServerSideSitemap**.

This will generate a xml file named same as the folder we created under pages i.e *server-sitemap.xml*.

Now build your next.js website using
`next build`

After successfull build,server sitemap will also get created and can be seen at:

`localhost:3000/server-sitemap.xml`

The above url lists the dynamic sitemaps.
The static sitemaps are created in public folder under the name of *sitemap* and *sitemap-0* and can be accessed using:

`localhost:3000/sitemap.xml`
`localhost:3000/sitemap-0.xml`

Make sure you add the above 2 files in .*gitignore* so that new files are created on the server on every build.

Get the complete Source Code **[here](https://github.com/leighhalliday/next-sitemap-demo)**.

That's it for today and See you guys in the next one!
Do comment in case of any issues.

Dynamic Sitemaps in NEXT.js | Generate URLs and Index Pages | 10X Traffic on Website

Hey devs,
Today we are going to implement  **Amazon Simple Queue Service** (SQS) with Spring Boot and see how messaging queues works in day to day of big techs.

Let's start by creating a skeleton Spring Boot Project.
You can Create a Spring boot application from **[here](https://start.spring.io/)**.

Now that your spring boot application is created now,you can open it in one of your IDEs and Now lets start coding step by step.

- As you all know first step in integrating any 3rd party package in our application is importing it first,Lets add this dependency in `pom.xml`.

```
<dependency>  
 <groupId>org.springframework.cloud</groupId>  
 <artifactId>spring-cloud-starter-aws-messaging</artifactId>  
 <version>2.2.6.RELEASE</version>  
</dependency>
```
 - Reload your project to make sure the dependency gets installed.
 - Lets setup our `application.properties` file with all our credentials.

```
cloud.aws.region.static=ap-south-1  
cloud.aws.region.auto=false  
cloud.aws.credentials.access-key=YOUR_ACCESS_KEY  
cloud.aws.credentials.secret-key=YOUR_SECRET_KEY 
cloud.aws.end-point.uri=YOUR_QUEUE_URL
```

You can generate all these credentials following this **[link](https://www.devdad.org/Post?title=AWS%20SQS%20Setup%20in%20Console%20%7C%20Users%20and%20Groups%20%7C%20Messaging%20Queues&id=6291e9bfa66f760004c10e6b)**.

 - Lets Create our Config file which spring boot can read and configure.

```
package com.springboot.demo.sqs.config;  
  
import com.amazonaws.auth.AWSStaticCredentialsProvider;  
import com.amazonaws.auth.BasicAWSCredentials;  
import com.amazonaws.client.builder.AwsClientBuilder;  
import com.amazonaws.services.sqs.AmazonSQSAsync;  
import com.amazonaws.services.sqs.AmazonSQSAsyncClientBuilder;  
import org.springframework.beans.factory.annotation.Value;  
import org.springframework.cloud.aws.messaging.core.QueueMessagingTemplate;  
import org.springframework.context.annotation.Bean;  
import org.springframework.context.annotation.Configuration;  
import org.springframework.context.annotation.Primary;  
  
@Configuration  
public class AwsSQSConfig {  
  
    @Value("${cloud.aws.region.static}")  
    private String region;  
  
    @Value("${cloud.aws.credentials.access-key}")  
    private String awsAccessKey;  
  
    @Value("${cloud.aws.credentials.secret-key}")  
    private String awsSecretKey;  
  
    @Value("${cloud.aws.end-point.uri}")  
    private String urlEndpoint;  
  
    @Bean  
  public QueueMessagingTemplate queueMessagingTemplate() {  
        return new QueueMessagingTemplate(amazonSQSAsync());  
    }  
  
    @Primary  
 @Bean  public AmazonSQSAsync amazonSQSAsync() {  
        AwsClientBuilder.EndpointConfiguration endpointConfig = new AwsClientBuilder.EndpointConfiguration(  
                urlEndpoint,  
                region  
  );  
        return AmazonSQSAsyncClientBuilder.standard()  
                .withEndpointConfiguration(endpointConfig)  
                .withCredentials(new AWSStaticCredentialsProvider(new BasicAWSCredentials(awsAccessKey, awsSecretKey)))  
                .build();  
    }  
  
  
}
```

![enter image description here](https://i.postimg.cc/SspXpJy0/carbon-SQS.png)

- In the above configuration file, we are first creating a `Bean` of **QueueMessagingTempelate** which will later be used for sending messages in the queue.
Then we are configuring the queue which we have created in AWS Console with its *name,region and user's access and secret kery.*

You can find a detailed explaination about setting SQS on console right [**here**](https://www.devdad.org/Post?title=AWS%20SQS%20Setup%20in%20Console%20%7C%20Users%20and%20Groups%20%7C%20Messaging%20Queues&id=6291e9bfa66f760004c10e6b).

- Now Lets Send and Receive messages using our queue.I have created this `Controller` class which has 1 endpoint which will help us send messages and 1 listener which will listen to that messsage and prints it in the console.

```
package com.springboot.demo.sqs.controllers;  
  
import org.slf4j.Logger;  
import org.slf4j.LoggerFactory;  
import org.springframework.beans.factory.annotation.Autowired;  
import org.springframework.beans.factory.annotation.Value;  
import org.springframework.cloud.aws.messaging.core.QueueMessagingTemplate;  
import org.springframework.cloud.aws.messaging.listener.annotation.SqsListener;  
import org.springframework.messaging.support.MessageBuilder;  
import org.springframework.web.bind.annotation.*;  
  
@RestController  
@RequestMapping("/sqs")  
public class SQSController {  
  
    @Autowired  
  private QueueMessagingTemplate queueMessagingTemplate;  
  
    @Value("${cloud.aws.end-point.uri}")  
    private String urlEndPoint;  
  
    Logger logger = LoggerFactory.getLogger(SQSController.class);  
  
    @GetMapping("/send/{message}")  
    public void sendMessage(@PathVariable String message){  
        logger.info("url{}",urlEndPoint);  
        queueMessagingTemplate.send(urlEndPoint, MessageBuilder.withPayload(message).build());  
    }  
  
    @SqsListener("demoQueue")  
    public void logMessage(String payload){  
         logger.info(payload);  
    }  
}
```

![enter image description here](https://i.postimg.cc/Xqcrs3Ff/carbon-SQS2.png)

As you can see in sendMessage method we are reading the message from the UrlParam and sending it in the queue and using a `SQSListener` with the name of the queue that we made to listen to all the messages we keep sending in that particular queue.

The queue we are sending messsages to is configured using **urlEndPoint** that we get from console while creating it. 

- Now open your browser and send a message like this:

`localhost:8080/sqs/send/testMessage`

you will see `testMessage` printed the console.

That's it for this Blog,Do comment down if you face any kind of error.
See you guys in the next one!

AWS SQS Integration with Spring Boot | Setting Up Messaging Queue | Producer and Consumer

Hey devs.
Today we are going to see how we can setup **Amazon Simple Queue Service** (SQS) in AWS Console.

**SQS** is a very popular messaging queue service which works on producer consumer model and is very popular among all the available messaging queue services like *Kafka*,*RabbitMQ* etc.

**Prerequisite**  : an activated AWS account.
Lets Setup SQS Step by Step:

- Open AWS Console.

![enter image description here](https://i.postimg.cc/s2jR1Mrz/image1aws.png)

- Enter SQS in the Search bar at the top.

![enter image description here](https://i.postimg.cc/13Pzc5QC/Screenshot-2022-05-28-at-10-49-04-AM.png)

- Select Simple Queue Service and click on *Create Queue*.

![enter image description here](https://i.postimg.cc/YSdBFtrW/Screenshot-2022-05-28-at-10-49-14-AM.png)

- On Clicking Create Queue a window will open asking for queue config details like name and all.

![enter image description here](https://i.postimg.cc/HxjD4FnP/Screenshot-2022-05-28-at-10-50-00-AM.png)

- Enter the Queue Name and skip all the configuration below:

![enter image description here](https://i.postimg.cc/w38CzvVS/Screenshot-2022-05-28-at-10-50-16-AM.png)

- Click on Create Queue and your queue is now created.

![enter image description here](https://i.postimg.cc/dtG1yZzZ/Screenshot-2022-05-28-at-10-50-24-AM.png)

![enter image description here](https://i.postimg.cc/wxCMMQbd/Screenshot-2022-05-28-at-10-50-35-AM.png)

- Now as the queue is now created, you also need to create a group and a user to further use that user in you APIs like *Spring Boot or Node.js*.Search for **IAM** in the search bar.

![enter image description here](https://i.postimg.cc/3xBxL5rK/Screenshot-2022-05-28-at-10-51-05-AM.png)

- Select IAM and then click on User Groups.

![enter image description here](https://i.postimg.cc/wvtxT1Xv/Screenshot-2022-05-28-at-10-51-19-AM.png)

A User group is basically a group where we add the permissions and configuration which users can later access by getting added to that group.

- Click on Create Group Button.

![enter image description here](https://i.postimg.cc/5tKNVBFT/Screenshot-2022-05-28-at-10-51-30-AM.png)

- Now under Create group,set the Group Name and add permissions to that group.You need to set 2 permissions here i.e *AmazonEC2Access and AdministratorAccess* and click on create Group.

![enter image description here](https://i.postimg.cc/MTh6cz5Y/Screenshot-2022-05-28-at-10-51-54-AM.png)

![enter image description here](https://i.postimg.cc/Hx7H1fm8/Screenshot-2022-05-28-at-10-52-50-AM.png)

![enter image description here](https://i.postimg.cc/gcZcC6ct/Screenshot-2022-05-28-at-10-53-08-AM.png)

- As the group has been successfully created,now its time to create a user and add it to this group.Click on **Users** in the left Column and click on **Add User**.

![enter image description here](https://i.postimg.cc/65x6t5yW/Screenshot-2022-05-28-at-10-53-39-AM.png)

![enter image description here](https://i.postimg.cc/ZntmbVY7/Screenshot-2022-05-28-at-10-53-51-AM.png)

- Add the user to the created group.

![enter image description here](https://i.postimg.cc/Rh7BNKNM/Screenshot-2022-05-28-at-10-54-00-AM.png)

- Now Click on next and confirm the user creation.

![enter image description here](https://i.postimg.cc/pdrRqm1Z/Screenshot-2022-05-28-at-10-54-10-AM.png)

![enter image description here](https://i.postimg.cc/fWmZ2n56/Screenshot-2022-05-28-at-10-54-20-AM.png)

- Now the user has been successfully created and now you can use the *Access Key* and *Secret Key* in your application and integrate with the SQS queues.

![enter image description here](https://i.postimg.cc/3R6ML9Dr/image2aws.png)

That's it for today,Next I will be writing a detailed article on how you can use queues in Spring Boot Servers with SQS Integration.

**See you guys soon!**

AWS SQS Setup in Console | Users and Groups | Messaging Queues

Hey devs.
In the previous blog,I explained how **HTTP** works in general and How **HTTPv2** is better than **HTTPv1**.

Today we are going to implement HTTPv2 on a **Node.js** server to see how our server can serve HTTPv2 requests.

## Step 1:
- Create a node.js project using `npm init`.
- This will create a skeleton node.js project and then create *index.js* where we will write our server.

## Step 2:
- http2 is available by default in npm **versions >=13**.
- Lets Create a server: 
 
       const http2 = require ("http2")
       const fs = require("fs")
       const server = http2.createSecureServer({
               "key": fs.readFileSync("localhost-private.pem"),
               "cert": fs.readFileSync("localhost-cert.pem")
       })
![enter image description here](https://i.postimg.cc/25bHMDzZ/carbon-httpsn1.png)

In the above snippet,we created a HTTPv2 server using **http2** package by npm.
As we want our server to be secure by SSL,we need to provide it a **SSL** Certificate.

To generate local key and cert you can use this command:

    openssl req -x509 -newkey rsa:4096 -nodes -sha256 -subj '/CN=localhost' -keyout localhost-private.pem -out localhost-cert.pem

![enter image description here](https://i.postimg.cc/vm241J93/carbon-httpsn4.png)

This will create 2 files beside index.js i.e *localhost-private.pem and -out localhost-cert.pem*.
Now using **fs** you can read key and cert from these files.

## Step 3:
- Now we need to listen to the server created above,As you guys know httpv2 server listens to request using *streams* as unlimited no of request are coming at once and the server listens to every single stream and recognize it using **stream IDs** which is further used to send response respectively.

      server.on("stream", (stream, headers) => {
      console.log(stream.id);
      
      // response headers
      stream.respond({
           "content-type": "application/json",
           "status": 200
       })
       
      //response bodies
       stream.end(JSON.stringify({
            "user": "devdad",
            "id": 823
       }))
        })
      server.listen(443);
      console.log("listening on port 443");

![enter image description here](https://i.postimg.cc/W305pwqp/carbon-httpsn2.png)

Now you can run this server and use it for http2 requests.
Here's complete **index.js** file:

    const http2 = require ("http2")
    const fs = require("fs")
    
    const server = http2.createSecureServer({
       "key": fs.readFileSync("localhost-private.pem"),
       "cert": fs.readFileSync("localhost-cert.pem")
    })
    
    server.on("stream", (stream, headers) => {
    console.log(stream.id);
    stream.respond({
       "content-type": "application/json",
       "status": 200
    })
    stream.end(JSON.stringify({
       "user": "devdad",
       "id": 823
    }))
    })
    
    server.listen(443);
    console.log("listening on port 443");

![enter image description here](https://i.postimg.cc/C5YmRnbG/carbon-httpsn3.png)

Now run your server and send request and check your http version in network tab.
That's **HTTPv2**.

That's it for today,See you guys in the next one!

HTTPv2 Server Implementation in Node.js | 90% Fast Servers

**HTTP** is a [protocol](https://developer.mozilla.org/en-US/docs/Glossary/Protocol) for fetching resources such as HTML documents. It is the foundation of any data exchange on the Web and it is a client-server protocol, which means requests are initiated by the recipient, usually the Web browser.

Clients and servers communicate by exchanging individual messages .The messages sent by the client, usually a Web browser, are called _requests_ and the messages sent by the server as an answer are called _responses_.

[![XqWvFS.md.png](https://iili.io/XqWvFS.md.png)](https://freeimage.host/i/XqWvFS)

The whole **OSI** (Open Systems Interconnection) layer is very vast and HTTP is just apart of it.
Multiple things happens in layers once we send a http connection like routing,encryption and decryption but our main focus here is Http and we will be deep diving into mechanics of **HTTP**.

Each individual request is sent to a server, which handles it and provides an answer called the _response_. Between the client and the server there are numerous entities, collectively called [proxies](https://developer.mozilla.org/en-US/docs/Glossary/Proxy_server), which perform different operations and act as gateway for example.

In reality, there are more computers between a browser and the server handling the request: there are routers, modems, and more. Thanks to the layered design of the Web, these are hidden in the network and transport layers. HTTP is on top, at the application layer. Although important for diagnosing network problems, the underlying layers are mostly irrelevant to the description of HTTP.

[![XqW8c7.md.png](https://iili.io/XqW8c7.md.png)](https://freeimage.host/i/XqW8c7)

In the above image as you can see,there are multiple components between a server and client like proxy i.e **Load Balancer** etc or Cache like **Redis** which get used by client for redundant and repetitive data.

**HTTP Request Structure.**
[![XCBVS9.md.png](https://iili.io/XCBVS9.md.png)](https://freeimage.host/i/XCBVS9)

- **Types of HTTP Requests:**
   - POST - Saving new Data into the DB.
   - GET - Fetching Data from DB.
   - PUT - replacing a data row in DB i.e Updating.
   - PATCH - Patching just specific columns in data row in DB.
   - DELETE - Deleting a data row in DB.
   - OPTIONS - Describes the communication options for the target resource i.e Server.

- **HTTP Status Codes:**
 HTTP Sttaus Codes are one of the most important part of this whole protocol system,It tells the client everything about whats going on with that HTTP Request.

[![XCCGWv.md.png](https://iili.io/XCCGWv.md.png)](https://freeimage.host/i/XCCGWv)

I have listed all the possible Status Codes HTTP Knows about with their respective meanings.

## 1xx Informational

100 Continue

101 Switching Protocols

102 Processing

## 2xx Success

200 OK

201 Created

202 Accepted

203 Non-Authoritative Information

204 No Content

205 Reset Content

206 Partial Content

207 Multi-Status (WebDAV)

208 Already Reported (WebDAV)

226 IM Used

## 3xx Redirection

300 Multiple Choices

301 Moved Permanently

302 Found

303 See Other

304 Not Modified

305 Use Proxy

306 (Unused)

307 Temporary Redirect

308 Permanent Redirect (experimental)

## 4xx Client Error

400 Bad Request

401 Unauthorized

402 Payment Required

403 Forbidden

404 Not Found

405 Method Not Allowed

406 Not Acceptable

407 Proxy Authentication Required

408 Request Timeout

409 Conflict

410 Gone

411 Length Required

412 Precondition Failed

413 Request Entity Too Large

414 Request-URI Too Long

415 Unsupported Media Type

416 Requested Range Not Satisfiable

417 Expectation Failed

418 I'm a teapot (RFC 2324)

420 Enhance Your Calm (Twitter)

422 Unprocessable Entity (WebDAV)

423 Locked (WebDAV)

424 Failed Dependency (WebDAV)

425 Reserved for WebDAV

426 Upgrade Required

428 Precondition Required

429 Too Many Requests

431 Request Header Fields Too Large

444 No Response (Nginx)

449 Retry With (Microsoft)

450 Blocked by Windows Parental Controls (Microsoft)

451 Unavailable For Legal Reasons

499 Client Closed Request (Nginx)

## 5xx Server Error

500 Internal Server Error

501 Not Implemented

502 Bad Gateway

503 Service Unavailable

504 Gateway Timeout

505 HTTP Version Not Supported

506 Variant Also Negotiates (Experimental)

507 Insufficient Storage (WebDAV)

508 Loop Detected (WebDAV)

509 Bandwidth Limit Exceeded (Apache)

510 Not Extended

511 Network Authentication Required

598 Network read timeout error

599 Network connect timeout error




- **How HTTP Works with TCP!**
   
   So Whenever a Client wants to establish a HTTP Connection,The Client needs to do a *TCP* Handshake with the server i.e a TCP Connection with the server.
   Now,A Browser can atmost establish *6 TCP Connections* at once,and until and unless all the 1 TCP Connection is served and free,no more TCP connections can be established hence no more HTTP Requests. So,HTTP Requests gets hold until and unless TCP tunnel is free.
Here's how it works:
[![XCo0Mv.md.png](https://iili.io/XCo0Mv.md.png)](https://freeimage.host/i/XCo0Mv)

In the above case as you can see,all the TCP connections are busy and hence no more HTTP Requests can be sent.
This is one of the major drawbacks of **HTTP v1.**

**AND HENCE COMES HTTPv2 with MultiPlexing !**

![XCoLVj.png](https://iili.io/XCoLVj.png)

Here's how you can check which HTTP Version your server is using:

![XCxMsj.png](https://iili.io/XCxMsj.png)

That's it for this Article,Comment down topics or any doubts you have.KEEP CODING!
Here are some common FAQ you can use:

## HTTP Method FAQs

### What’s the difference between PUT and POST?

`PUT`  requests are idempotent, meaning that executing the same  `PUT`  request will always produce the same result.

On the other hand, a  `POST`  will produce different outcomes. If you execute a  `POST`  request multiple times, you'll create a new resource multiple times despite them having the same data being passed in.

Using a restaurant analogy,  `POST`ing multiple times would create multiple separate orders, whereas multiple  `PUT`  requests will update the same existing order.

### What’s the difference between PUT and PATCH?

The key differences are that  `PUT`  will create a new resource if it cannot find the specified resource. And with  `PUT`  you need to pass in data to update the entire resource, even if you only want to modify one field.

With  `PATCH`, you can update part of a resource by simply passing in the data of the field to be updated.

### What if I just want to update part of my resource? Can I still use PUT?

If you just want to update part of your resource, you still need to send in data for the entire resource when you make a  `PUT`  request. The better-suited option here would be  `PATCH`.

### Why is a body optional for a request and response?

A body is optional because for some requests, like resource retrievals using the  `GET`  method, there is nothing to specify in the body of your request. You are requesting all data from the specified endpoint.

Similarly, a body is optional for some responses when a status code is sufficient or there is nothing to specify in the body, for example with a  `DELETE`  operation.

HTTP Explained | HTTP Requests and Status Codes | HTTP with TCP | HTTPv1 vs HTTPv2

Software Development Job Openings 👇🏻
[Walmart, Revolut, Gojek, and Y Combinator]

**Walmart Global Tech**
Frontend Engineer
Link: [https://bit.ly/3ynYU9a](https://www.linkedin.com/jobs/view/3069175408/)

**Y Combinator**
YC Internship Program
Link: [https://bit.ly/3wkx0Ij
](https://www.workatastartup.com/internships)

**Gojek**
Software Engineer
Link: [https://bit.ly/3N2N6x5](https://jobs.lever.co/gojek/4f8baea9-35b3-454d-a04f-bd750c4823db?lever-)

**Revolut**
Software Engineer
Link: [https://bit.ly/3FuE09W](https://jobs.lever.co/revolut/c205df29-3419-4a53-9015-02c17346cdb8?lever-)

Follow devdad to stay updated with the daily job alerts and more !

Software Development Job Openings | Placements | devdad

**How does the Internet work?**

Great question! The Internet's growth has become explosive and it seems impossible to escape the bombardment of www.com's seen constantly on Social Media. Because the Internet has become such a large part of our lives, a good understanding is needed to use this new tool most effectively.

As Internet is a global network of computers,it is very important that each computer must be uniquely identified.Hence comes the **IP Address**.

IP addresses are in the form nnn.nnn.nnn.nnn where nnn must be a number from 0 - 255.
The picture below illustrates two computers connected to the Internet; your computer with IP address 1.2.3.4 and another computer with IP address 5.6.7.8. The Internet is represented as an abstract object in-between.

![](https://web.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper_files/ruswp_diag1.gif)

As you all must have a Wifi Internet connection at one which in technical terms called an ISP- Internet Service Provider. Everytime you connect to your wifi,your computer is assigned a temporary IP address which uniquely identifies your computer in that network.

**How Computers Talk?**

Computers in a network be it LAN network or Internet Network communicates through a particular set of protocols.

- Application Protocol
- Transmission Protocol
- Internet Protocol
- Hardware Protocol

**Communication Process!**

![](https://web.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper_files/ruswp_diag2.gif)

1.  The message would start at the top of the protocol stack on your computer and work it's way downward.
2.  If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data. This is because data sent over the Internet (and most computer networks) are sent in manageable chunks. On the Internet, these chunks of data are known as **packets**.
3.  The packets would go through the Application Layer and continue to the TCP layer. Each packet is assigned a **port number**. Ports will be explained later, but suffice to say that many programs may be using the TCP/IP stack and sending messages. We need to know which program on the destination computer needs to receive the message because it will be listening on a specific port.
4.  After going through the TCP layer, the packets proceed to the IP layer. This is where each packet receives it's destination address, 5.6.7.8.
5.  Now that our message packets have a port number and an IP address, they are ready to be sent over the Internet. The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the phone line.
6.  On the other end of the phone line your ISP has a direct connection to the Internet. The ISPs **router** examines the destination address in each packet and determines where to send it. Often, the packet's next stop is another router. More on routers and Internet infrastructure later.
7.  Eventually, the packets reach computer 5.6.7.8. Here, the packets start at the bottom of the destination computer's TCP/IP stack and work upwards.
8.  As the packets go upwards through the stack, all routing data that the sending computer's stack added (such as IP address and port number) is stripped from the packets.
9.  When the data reaches the top of the stack, the packets have been re-assembled into their original form, "Hello computer 5.6.7.8!"

**How Computers Identify each other?**

But what if you don't know the IP address of the computer you want to connect to? What if the you need to access a web server referred to as www.othercomputer.com? How does your web browser know where on the Internet this computer lives? The answer to all these questions is the Domain Name Service or DNS. The DNS is a distributed database which keeps track of computer's names and their corresponding IP addresses on the Internet.
Many computers connected to the Internet host part of the DNS database and the software that allows others to access it. These computers are known as DNS servers. No DNS server contains the entire database; they only contain a subset of it. If a DNS server does not contain the domain name requested by another computer, the DNS server re-directs the requesting computer to another DNS server.

So,DNS is basically a kind of Database that stores all the domain names corresponding to their IP Addresses and whenever you want to connect to suppose 10.8.9.100 then it looks up domain of 10.8.9.100 and connects to corresponding domain of it like www.othercomputer.com.

So,Thats it for the basic introduction of how internet works in general.See you guys in the next one!

How Internet Works Explained in Easy Steps | by devdad

Hello Everyone,devdad This side :)

#### Why We need Binary Search:-

1.  After DP and Graph , Binary Search is one of the most asked interview topic in top product base companies.
2.  In some DP question you need to use Binary Search
3.  Binary Search also usefull in Binary Search Tree Concept

### Topic wise learning of Binary Search:

-   Phase 1 : Normal Queastion like next element, finding ceil or floor, find first or last occurance of a number, LowerBound and UpperBound. (sometimes companies like microsoft don't give you permission to use STL/Collection Framework for lower bound and upper bound)
-   Phase 2 : Update your binary search algorithm in some mathematical questions like ternary search, square root of a num, search element in a infinite array, find peak element, search in matrix.
-   Phase 3 : Circular array type questions like Find min element in a ciculary sorted array, find number of rotate a sorted array elements, search in rotate and sorted array, search in a nearly sorted array, Minimum difference element in an sorted array.
-   Phase 4 : Biotonic array related questions max eleemnt in a biotonic array, search element in biotonic array.
-   Phase 5 : where you need to master in Binary Search, for that do some tricky questions- Magnetic Force Between Two Balls, Minimum Limit of Balls in a Bag, Minimized Maximum of Products Distributed to Any Store , Capacity To Ship Packages Within D Days, Maximum Candies Allocated to K Children .

### Quality Questions Step by Step practice:-

Easy:-\
<https://leetcode.com/problems/sqrtx/>\
<https://leetcode.com/problems/binary-search/>\
<https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix/>\
<https://leetcode.com/problems/peak-index-in-a-mountain-array/>

Medium:-\
<https://leetcode.com/problems/time-based-key-value-store/>\
<https://leetcode.com/problems/search-in-rotated-sorted-array/>\
<https://leetcode.com/problems/powx-n/>\
<https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/>\
<https://leetcode.com/problems/find-peak-element/>\
<https://leetcode.com/problems/search-a-2d-matrix/>\
<https://leetcode.com/problems/divide-two-integers/>\
<https://leetcode.com/problems/capacity-to-ship-packages-within-d-days/>\
<https://leetcode.com/problems/minimum-limit-of-balls-in-a-bag/>

Hard:-\
<https://leetcode.com/problems/median-of-two-sorted-arrays/>\
<https://leetcode.com/problems/count-of-smaller-numbers-after-self/>\
<https://leetcode.com/problems/max-sum-of-rectangle-no-larger-than-k/>\
<https://leetcode.com/problems/split-array-largest-sum/>\
<https://leetcode.com/problems/shortest-subarray-with-sum-at-least-k/>

Youtube Videos Recommendation :

1.  <https://youtube.com/playlist?list=PL_z_8CaSLPWeYfhtuKHj-9MpYb6XQJ_f2> [Aditya Verma, Language- Hindi]
2.  <https://youtube.com/playlist?list=PLgUwDviBIf0qYbL4TBaEWgb-ljVdhkM7R> [Striver , Language- English]
3.  Live Classes of striver :-

-   <https://www.youtube.com/watch?v=SpS9dMj0B_Y>
-   <https://www.youtube.com/watch?v=B4t3NB0478k>
-   <https://www.youtube.com/watch?v=Kb3KOTQfjew>

Happy Coding, Happy Learning.\
PS - If You want more topics like that and also find this helpful then please comment down. And tell which topic you want next!

Master Binary Search | Full Guide | Placement Preparation | devdad

Software Development Job Openings for the day 👇🏻
[LinkedIn, redBus, Glance, and Udaan]

LinkedIn
Software Engineer
Link: [https://www.linkedin.com/jobs/view/3066311334/](https://www.linkedin.com/jobs/view/3061598625/)

redBus
Software Engineer
Link: [https://www.redbus.in/careers/jobsdesc?jobid=a6246d13f65564](https://www.linkedin.com/jobs/view/3061598625/)

Glance
Software Development Engineer I
Link: [https://boards.greenhouse.io/glance/jobs/3823801](https://boards.greenhouse.io/glance/jobs/3823801)

Udaan
Software Engineer
Link: [https://www.linkedin.com/jobs/view/3061598625/](https://boards.greenhouse.io/glance/jobs/3823801)

Follow devdad to stay updated with the daily job alerts!

Software Development Job Openings | LinkedIn, redBus and more | devdad

Software Development Job Openings for the day 👇🏻
[Microsoft, Twilio, Nutanix, and JP Morgan and more]

**Microsoft**
Software Engineer
Link: [https://lnkd.in/guUS8Y7n](https://lnkd.in/guUS8Y7n)

**Salesforce**
Software Engineer [AMTS]
Link: [https://lnkd.in/gwRzT8dq](https://lnkd.in/gwRzT8dq)

**Nutanix**
Member of Technical Staff
Link: [https://lnkd.in/g_a3tV3m](https://lnkd.in/g_a3tV3m)

**Grab**
Senior Software Engineer
Link: [https://lnkd.in/gaWt8Z_u](https://lnkd.in/gaWt8Z_u)

**Twilio**
Software Engineer
Link: [https://lnkd.in/gddCBNNH](https://lnkd.in/gddCBNNH)

**Postman**
Software Engineer 1
Link: [https://lnkd.in/gStY9HJh](https://lnkd.in/gStY9HJh)

**JPMorgan Chase & Co.**
Software Engineer
Link: [https://lnkd.in/ghU3_saa](https://lnkd.in/ghU3_saa)

**Meesho**
Software Development Engineer II
Link: [https://lnkd.in/gdGk9Qid](https://lnkd.in/gdGk9Qid)

Follow devdad to stay updated with the daily job alerts!

Software Development Job Openings | Placements and Job Opportunities | devdad

```
The number of questions are a lot and difficulty level of most of them are hard.
Don't flatter yourself completing every questions.
Take a few detours to other topics.

```

[Github Solutions](https://github.com/xahinds2/DataStructures/blob/main/04_graph_I.md)\
Graph Problems : <https://leetcode.com/list/9ftzxgem>\
DSU Union Find : <https://leetcode.com/list/9ftztxv7>

BFS & DFS problems

1.  Flood Fill : <https://leetcode.com/problems/flood-fill/>
2.  Number of Islands : <https://leetcode.com/problems/number-of-islands/>
3.  Max Area of Island : <https://leetcode.com/problems/max-area-of-island/>
4.  Number of Closed Islands : <https://leetcode.com/problems/number-of-closed-islands/>
5.  Number of Enclaves : <https://leetcode.com/problems/number-of-enclaves/>
6.  Count Sub Islands : <https://leetcode.com/problems/count-sub-islands/>
7.  As Far from Land as Possible : <https://leetcode.com/problems/as-far-from-land-as-possible/>
8.  Word Ladder : <https://leetcode.com/problems/word-ladder>
9.  Rotting Oranges : <https://leetcode.com/problems/rotting-oranges/>
10. Coloring A Border : <https://leetcode.com/problems/coloring-a-border/>
11. Pacific Atlantic Water Flow : <https://leetcode.com/problems/pacific-atlantic-water-flow/>
12. Shortest Path in Binary Matrix : <https://leetcode.com/problems/shortest-path-in-binary-matrix/>
13. 01 Matrix : <https://leetcode.com/problems/01-matrix/>
14. Shortest Bridge : <https://leetcode.com/problems/shortest-bridge/>
15. Nearest Exit from Entrance in Maze : <https://leetcode.com/problems/nearest-exit-from-entrance-in-maze/>
16. Cut Off Trees for Golf Event: <https://leetcode.com/problems/cut-off-trees-for-golf-event/>
17. Longest Increasing Path in a Matrix: <https://leetcode.com/problems/longest-increasing-path-in-a-matrix/>

Graph Theory problems

1.  Keys and Rooms : <https://leetcode.com/problems/keys-and-rooms/>
2.  Find the Town Judge : <https://leetcode.com/problems/find-the-town-judge/>
3.  Time Needed to Inform All Employees : <https://leetcode.com/problems/time-needed-to-inform-all-employees/>
4.  Minimum Number of Vertices to Reach All Nodes : <https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/>
5.  Is Graph Bipartite : <https://leetcode.com/problems/is-graph-bipartite/>
6.  Possible Bipartition : <https://leetcode.com/problems/possible-bipartition/>
7.  Find Eventual Safe States: <https://leetcode.com/problems/find-eventual-safe-states/>
8.  Bus Routes : <https://leetcode.com/problems/bus-routes/>

Union Find & Connected components problems

```
// standard template for DSU
class DSU {
public:
    vector<int> root;
    vector<int> rank;

    DSU(int n){
        root = vector<int>(n,-1);
        rank = vector<int>(n, 1);
    }

    int find(int x) {
        if(root[x] == -1) return x;
        return root[x] = find(root[x]);
    }

    void merge(int x, int y) {
        int rx = find(x);
        int ry = find(y);

        if(rx == ry) return;
        if(rank[rx] >= rank[ry]) {
            root[ry] = rx;
            rank[rx] += rank[ry];
        } else {
            root[rx] = ry;
            rank[ry] += rank[rx];
        }
    }
};

```

```
union : connect two nodes and appoint a parent using ranks
find : return the parent of a node

```

1.  Number of Provinces: <https://leetcode.com/problems/number-of-provinces/>
2.  Surrounded Regions: <https://leetcode.com/problems/surrounded-regions/>
3.  Redundant Connection: <https://leetcode.com/problems/redundant-connection/>
4.  Redundant Connection II: <https://leetcode.com/problems/redundant-connection-ii/>
5.  Number of Operations to Make Network Connecte: <https://leetcode.com/problems/number-of-operations-to-make-network-connected/>
6.  Largest Component Size by Common Factor: <https://leetcode.com/problems/largest-component-size-by-common-factor/>
7.  Accounts Merge: <https://leetcode.com/problems/accounts-merge/>
8.  Most Stones Removed with Same Row or Column : <https://leetcode.com/problems/most-stones-removed-with-same-row-or-column/>
9.  Minimize Malware Spread : <https://leetcode.com/problems/minimize-malware-spread/>
10. Regions Cut By Slashes : <https://leetcode.com/problems/regions-cut-by-slashes/>

Dijkstra :

```
* build adj structure
* stores time of that n nodes
* intialise the time with infinity for the algorithm to work
* Time for starting node is 0
* using priority_queue travel to the smallest weights
* Broadcast the signal to adjacent nodes if(reqd time < initial time)
* keep on adding the previous weights with curr weight and
* keep on going forward it the weight keeps on decreasing

```

1.  Network Delay Time : <https://leetcode.com/problems/network-delay-time/>
2.  Cheapest Flights Within K Stops: <https://leetcode.com/problems/cheapest-flights-within-k-stops/>
3.  Path with Maximum Probability: <https://leetcode.com/problems/path-with-maximum-probability/>
4.  Path With Minimum Effort: <https://leetcode.com/problems/path-with-minimum-effort/>
5.  Swim in Rising Water: <https://leetcode.com/problems/swim-in-rising-water/>

Bellman ford

```
* It gives us shortest distance in terms of no. of edges
* shortest path in k steps (k- length eges will be traveled)
* so to get shortest path in k edges, algo has to be run until k times
* specially problems with limting edges and also detects negative eight cycle

```

1.  Network delay time : <https://leetcode.com/problems/network-delay-time/>
2.  Cheapest Flights Within K Stops: <https://leetcode.com/problems/cheapest-flights-within-k-stops/>

Minimum Spanning Tree

```
Prims (works only in connected graph):
* mst is always formed using n-1 edges
* use priority_queue to get edge of minimum weight
* mark them visited and add their weight to res

Kruskal (works faster in disconected, sparse graph) :
* sort the edges wrt weights
* loop over the edges and connect them one by one
* if it does not form cycle (use DSU to detect)

```

1.  Min Cost to Connect All Points: <https://leetcode.com/problems/min-cost-to-connect-all-points/>
2.  Connecting Cities With Minimum Cost: <https://leetcode.com/problems/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree/>

Topological Sort

```
* make indegree array and adj list
* put all the 0 indegree in queue and mark them visited
* and keep on trveling to their dependents and decrease their indegree
* also add it to queue if their indegree is 0 (indegree == dependency number)
* and loop it until the queue filled in 1st step gets empty
* if (every nodes are visited then you can finish all courses)

```

1.  Course Schedule : <https://leetcode.com/problems/course-schedule/>
2.  Course Schedule II: <https://leetcode.com/problems/course-schedule-ii/>
3.  Alien Dictionary: <https://leetcode.com/problems/alien-dictionary/solution/>

Tarjan's Algo

```
* build adj list
* make two arrays disc and low
* disc[i] stores time at which (i) got discovered
* low[i] stores the lowest discovery value which it can touch
* dfs on undiscovered nodes while backtracking check
* if their next node can't touch itself or its previous nodes
* that means that their edge is critical

```

1.  Strongly Connected Components : <https://leetcode.com/problems/critical-connections-in-a-network/>

Flyod warshall

```
* make a dp array with biggest number
* and make i -> i = 0 (shortest dist = 0)
* and fill the rest of index as given in question
* try minimising by traveling to i index in between

```

```
        for(int i=0; i<n; i++)
        for(int j=0; j<n; j++)
        for(int k=0; k<n; k++){
            dp[j][k] = min(dp[j][i] + dp[i][k], dp[j][k]);
        }

```

`* using for loop check for less counts from each index`

1.  Network delay time: <https://leetcode.com/problems/network-delay-time/>
2.  Sliding Puzzle : <https://leetcode.com/problems/sliding-puzzle/>
3.  Find the City With the Smallest Number of Neighbors: <https://leetcode.com/problems/find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance/>

Miscellenous :

1.  Remove Max Number of Edges to Keep Graph Fully Traversable : <https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable/>
2.  Critical Connections in a Network : <https://leetcode.com/problems/critical-connections-in-a-network/>
3.  Reconstruct Itinerary : <https://leetcode.com/problems/reconstruct-itinerary/>
4.  Sentence Similarity : <https://leetcode.com/problems/sentence-similarity/> or <https://nados.io/question/sentence-similarity?zen=true>
5.  Minimize Hamming Distance After Swap Operations : <https://leetcode.com/problems/minimize-hamming-distance-after-swap-operations/>
6.  Satisfiability Of Equality Equation : <https://leetcode.com/problems/satisfiability-of-equality-equations/>
7.  Rank Transform Of A Matrix Hard : <https://leetcode.com/problems/rank-transform-of-a-matrix/>

List of problems : <https://leetcode.com/list/9dx303n3>

Graph for Beginners | Problems and Patterns | Data Structures and Algorithms

1\. Vector

-   Intitalisation

    ```
    vector<int> v; /* Empty */
    vector<int> v( size ); /* Vector with size 'size' */
    vector<int> v( size, value ); /* Vector with size 'size' and all elements with value 'value' */

    ```

-   Basic Inbuilt Functionalities

    ```
    v.size(); /* Get size of vector */
    v.resize( size, value ); /* Fills the additional size of vector with value 'value' */
    v.empty(); /* returns true if vector is empty */
    v.front(); or v[0]; /* Accessing first element */
    v.back(); or v[v.size()-1]; /* Accessing last element */

    ```

-   Insert an element or a range

    ```
    v.push_back( ele ); /* Add an element 'ele' to the end */
    v.insert( v.begin() + i, ele ); /* Inserting element 'ele' at index i | Use i = 0 for inserting at front */
    v.insert( v.end(), v2.begin(), v2.end() ); /* Inserting the elements of vector 'v2' to the end of vector 'v' */

    ```

-   Erase an element or range

    ```
    v.pop_back(); /* Remove element at end */
    v.erase( v.begin() + i ); /* Remove element at index i */
    v.erase( v.begin() + i, v.begin() + j ); /* Remove elements from index i to j-1 */
    v.erase( remove( v.begin(), v.end(), value ), v.end() ); /* Removes all elements with value 'value' from the vector */

    ```

2\. Strings

-   Intitalisation

    ```
    string s; /* Empty string */
    string s_copy(s); or string s_copy = s; /* string with same value as s */

    ```

-   Inbuilt Functionalities

    ```
    /* All vector functionalities also apply to strings. */
    s.find( search_string ); /* Finds first occurence of search_string in s, returns -1 if not present. */
    s.find( search_string, start_pos ); /* Finds first occurence of search_string in s - starting from index start_pos , returns -1 if not present */

    ```

-   String to Numbers and Vice Versa

    ```
    string str = "12345";
    int num_str = stoi(str); /* To convert str"s value into integer and store it in integer num_str */
    /* Similarly for long long we have stoll(str)
    For vice versa, we have: */
    string str = to_string(num_str); /* To convert num_str's value into integer and store it in string str */

    ```

-   String Streams

    1.  Count words

        ```
        string str = "Hello World";
        stringstream ss (str); /* In this way, you can initialise a string stream with str's value */

        int count = 0;
        string word;
        /* ss >> var will perform as if we are doing cin>>var with the input as the value of 'ss'
        If you do ss >> word, think of it like ss throws it's first word into 'word' */
        while( ss >> word ){
        	cout<<word<<'-';
        	count++;
        }
        cout<<count;
        Output : Hello-World-2

        ```

    2.  Converting String to Numbers

        ```
        string str = "12345";
        stringstream ss (str);
        /* ss >> var will perform as if we are doing cin>>var with the input as the value of 'ss' */
        int x;
        ss>>x; /* x will now have value 12345 */

        ```

    3.  Split Functionality by changing delimiter

        ```
        /* For this we take help of getline function to change the default delimiter from ' ' to  '-'
        getline(istream& is, string& str, char delim); */
        stringstream ss( "123-456-789");
        vector<string> v;
        string word;
        while( getline(ss, word, '-') ){
        	v.push_back(word);
        }
        /* v will now have value : {"123", "456", "789"} */

        ```

3\. STL Helper Functions

```
vector<Type> v;

```

-   Sort

    ```
    /*
    	Default sort behaviour : Increasing, by Type :
    	int : by value
    	pair<int, int> : First by first value , then by second value
    	vector<int> or string : Lexicographically
    */

    sort( v.begin(), v.end() ); // Standard Increasing Sort

    static bool customComparator(const Type &obj1, const Type &obj2 ){
    	/* Think of obj1 and obj2 as two adjacent elements in the final sorted array
    	  where obj1 comes before obj2, Just write the relation you want between obj1 and obj2.
    	  For eg : Let the type be int If you want smaller value to come first, write : return obj1<obj2.
    	  Another eg : Let the type be vector<int> and If you want the vector with larger value at
    	  index 3 to come first write : return obj1[3] > obj2[3] */
    	return * logic * ;
    }
    sort( v.begin(), v.end(), customComparator ); /* Sort with customComparator */

    ```

-   Reverse

    ```
    reverse( v.begin(), v.end() ); /* Reverse the vector/string */

    ```

-   Minimum and Maximum Element

    ```
    auto it = min_element( v.begin(), v.end() );
    /* To get positon do it-v.begin()
       To get value do *it
       Similarly use max_element for maximum */

    ```

-   Binary Search

    ```
    /* The array must be sorted in increasing order for binary search */
    lower_bound( v.begin(), v.end(), ele ); /* Lower Bound : Returns iterator to first element >=ele */
    upper_bound( v.begin(), v.end(), ele ); /* Upper Bound : Returns iterator to first element >ele */
    binary_search( v.begin(), v.end(), ele ); /* binary_search : Return true if element 'ele' is found */

    ```

-   Sum

    ```
    int array_sum = accumulate( v.begin(), v.end(), initial_sum ); /* Set initial_sum as 0 for taking sum of the array */

    ```

-   Next Permutation

    ```
    next_permutation( v.begin(), v.end() ); /* Shifts the vector/string to its next permutation in O(n) */
    ```

C++ STL Guide for online Coding Rounds | by devdad

```
LET`S DISCUSS ABOUT BITWISE OPERATORS ,IF U READ THIS ARTICLE U WILL GET SOLID KNOWLEDGE IN BIT MANIPULATION.LET`S GET STARTED.
IT IS A LONG ARTICLE ,BUT IF YOU READ IT WITH PATIENCE IT WILL HELP A LOT.

```

```
What Is Binary Number System?
Ans)It Is a Numbering System Mainly Used In Computer Field,
Bcoz Computers Does Not Understand Human Language .
And It Only Understands Electrical Signals Through Transistors.Hence Our Computer Scientist`s Introduced Binary System.
In This Binary Number System 1 Means Transistor Is On and 0 Means Transistor Is Off [Does Not Glow].

```

```
Let`s Discuss Some Operators Known As Bitwise Operators Which Manipulate the Numbers.They are:
1. Bitwise AND(&)
2. Bitwise OR(|)
3. Bitwise XOR(^)
4. Left Shift(<<)
5. Right Shift(>>)
6. ~

```

```
Let`s Discuss Them One By One With Some Examples.

```

```
1.Bitwise AND,Keyword="&";

What & Operator Does?

It takes Two Bits At A Time .IF Both Bits Are Set Then It Returns 1 Else Returns 0.
Lets See Truth Table.
[ 1 ] [ 1 ]  = 1
[ 1 ] [ 0 ]  = 0
[ 0 ] [ 1 ]  = 0
[ 0 ] [ 0 ]  = 0

Let`s See Some Examples .

1)Check Whether A Number Is Odd Or Not Without Using % Operator?

Note.*For Odd Numbers They Have 1st Right Bit As Set In Binary Representation.
     * For Even Numbers They Have 1st Right Bit As Set In Binary Representation.
When we Perform & With One[1], If We Get Result As 1 Then It Is Odd Number Else It Is Even.
 For Simplicity We Take 4 Bits To Represent.
			   0011
			 & 0001
			   ---
			   01 The Result Is 1 Hence It Is Odd.

			   0010
			 & 0001
			 ------
			 00 The Result Is 0 Hence It Is Even.

Let`s See Program

int main()
{
int a;
cin>>n;
if(c&1) cout<<"It Is Odd Number";

else cout<<"It Is Even Number".
}

```

```
2.Bitwise OR[ | ]

It Checks Two Bits At A Time .If Any Of The Bits Is Set It Results One ,If Both Are Zero It Results Zero. Let`s See Truth Table.

[ 1 ] [ 1 ]=[ 1 ]
[ 1 ] [ 0 ]=[ 1 ]
[ 0 ] [ 1 ]=[ 1 ]
[ 0 ] [ 0 ]=[ 0 ]

```

```
3.Bitwise XOR[ ^ ]

It is Important Operator In Bit Manipulation And Most Of The Interview Questions On Bit Manipulation Depends On XOR Operator.
It Takes Two Bits At a Time ,If Both Bits Are Different It Results One Else Zero.
Let`s See Truth Table

[ 1 ] [ 1 ]=[ 0 ]
[ 1 ] [ 0 ]=[ 1 ]
[ 0 ] [ 1 ]=[ 1 ]
[ 0 ] [ 0 ]=[ 0 ]

Let`s See Some Most Most Important Properties Of XOR.

1.XOR WITH ZERO RESULTS SAME NUMBER Ex:A^ZERO=A;

2.XOR WITH SAME NUMBER RESULTS ZERO Ex:A^A=0;

3.A^B==B^A;

4.A^(B^C)=B^(A^C)

 Let`s See Some Questions Related To XOR.

1)SINGLE NUMBER[136 IN LEETCODE]

DESCRIPTION :Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

LETS USE THE SECOND PROPERTY [XOR WITH SAME NUMBER IS ZERO].

 int single(vector<int>&nums)
 {
 int res=nums[0];
 for(int i=1;i<nums.size();i++)
 {
 res^=nums[i];
 }
 return res;
 }

 THE INTUITION IS THE NUMBER WHICH APPEARED TWICE WILL CANCEL EACH OTHER AND THE NUMBER WHICH HAS OCCURED ONCE WILL BE IN RES VARIABLE .

2)MINIMUM NUMBER OF FLIPS TO CONVERT A TO B.
FLIP means Changing 0 to 1 Viceversa.

We know How XOR works,Let Take XOR Of Two Numbers And Count Set Bits In The Result,
What The Intutin Behind Counting Set bits After Taking XOR ,If We Want To Convert A TO B we Want To Make ALL BIT Positions Of A equal To B,When We Take XOR If Two Bits Are Different Then Result Is One ,which Says That We Want To flip one Bit.
Let`s See The Program

int main()
{
int a,b,flips=0;
cin>>a>>b;
int res=a^b;
//counting set bits using predefined function;

flips=_builtin_pop_count(res)//A PreDefined Function In GCC Compiler To Count Number Of Set Bits In A Number,It returns Integer.

//counting set bits without predefined function.
while(res)
{
if(res&1==1)flips++;
res=res>>1;//RIGHT SHIFT OPERATOR SEE BELOW WE DISCUSSED CLEARLY.
}
cout<<flips;
}

3)Check Number Is Odd Or Even Using XOR Operator.

Let`s See The Program

int main()
{
int a;
cin>>n;
int res=a^1;
if(res==a-1)cout<<"GIVEN NUMBER IS ODD"

else cout<<"GIVEN NUMBER IS EVEN";
}
WHAT THE INTUTION 🤔🤔🤔I WILL LEAVE FOR U THINK WELL.

```

```
4.LEFT SHIFT OPERATOR[<<].

It Is Also An Important Operator.

THE MOTTO OF LEFT SHIFT OP IS IT SHIFTS THE BITS BY I POSITONS LEFT.Lets see How it Works.
Let`s Take A 8 BIT Number For Simplicity And that Number Is 3.
[0]0000011
now 3<<1 Means The Last BIT goes OFF AND New ZERO WIll BE added At right.
0000011[0]
        ☝  NEW BIT IS ADDED AT RIGHT.
Important Properties Of LEFT SHIFT Op are.

1)Left Shifting A Number i Times Then The Number Becomes N=N*pow(2,i);//predefined Pow Function.

2)If We Left Shift A Number By One It Is Same as Multiplying A Number By  2,that`s Why We Use It In Competitive Programming Bcoz Bitwise Op`s Are Faster Than Arthimetic Op`s.

LET`S See Some Questions ON Left Shift.

1)Multiply A Number With 2 Without Using "*" Operator.
Program
int main()
{
int a;
cin>>a;
int res=a<<1;
cout<<res;
}

2)Multiply A Given Number With 3?

It`s A tricky Question But It`s An Easy One Let`s Derive An Formula.
Let Consider A Number a=3,Now when Multiplied By 3 Then It Becomes 9.

Let`s Bring Some Math Here

 We Want  3*a
 3a Can Be Written As 4a-a .

 Let`s Think How we Can Get 4a By USING LEFT SHIFT OP,[by left shifting 2 times am i correct]

 Let`s Write A Program.

 int main()
 {
 int a;
 cin>>a;
 int k=3;
 int temp=a;
 a=a<<2;//NOW A=12;
 cout<<a-temp;//CONSOLE DISPLAYS 9;
 }
 HEY Readers Let`s Try The Same Logic But Now K=7 .NOTE[ALWAYS K+1 IS POWER OF 2,LIKE 3,7,15,31 ETC];

 3)Check Whether i TH Bit Is Set Or Not?

 Step1:Left Shift 1 by i times.
 Step2:TAKE & With One After Left Shifting i Times .
 Let`s See The Program.

 int main()
 {
 int a,i;
 cin>>a>>i;
 int temp=1;
 temp=temp<<i;
 if(a&temp)cout<<"i TH BIT IS SET";

 else cout<<"i TH BIT IS NOT SET".
 }

```

```
5.RIGHT SHIFT OPERATOR[>>]

THE MOTTO OF RIGHT SHIFT OP IS IT SHIFTS THE BITS BY I POSITONS RIGHT.Lets see How it Works.
Let`s Take A 8 BIT Number For Simplicity And that Number Is 3.
0000001[1]
now 3>>1 Means The FIRST[FROM RIGHT] BIT goes OFF AND New ZERO WIll BE added At LEFT.
[0]0000001
☝  NEW BIT IS ADDED AT LEFT.
Important Properties Of RIGHT SHIFT Op are.

1)RIGHT Shifting A Number i Times Then The Number Becomes N=N/pow(2,i);//predefined Pow Function.

2)If We Right Shift A Number By One It Is Same as Dividing[FLOOR DIVISION] A Number By  2.

LET`S  SEE SOME QUESTIONS ON RIGHT SHIFT OP.

1)DIVIDE A NUMBER BY 2 WITHOUT USING "*" OPERATOR.
Let`s See The Program.

int main()
{
int a=4
cin>>a;
cout<<a>>1;//CONSOLE DISPLAYS [4/2]=2;
}

2.Count Number Of Set Bits In A Number.[We Already Discussed Above ,MIN Flips to convert A TO B].

```

```
6)~ OPERATOR.

 It is An Simple operator It Flips ALL The Bits Of A Number And It Takes Only One Parameter.
 EX:~a;

```

```
HOPE U LIKED THIS POST/ARTICLE .
IF U PRACTICE AFTER READING THIS U WILL GET A SOLID KNOWLEDGE IN BIT MANIPULATION.
🔥🔥🔥
```

COMPLETED GUIDE ON BITWISE OPERATORS | DSA

*`This post is intended to guide you on how to practice leetcode problems efficiently. Getting an AC is not enough, efficient practice is way more than that. Real learning starts only after you got the first AC or TLE`*.

I want you to remember this image throughout your leetcode journey.\
![image](https://assets.leetcode.com/users/images/395d87be-3fc1-436a-9b7e-cc781cac3f6e_1651737499.809321.jpeg)

Why follow the advice listed in this post?
------------------------------------------

-   Whatever I suggest in this post is from my 1-year of experience at leetcode and learnings. It will be *`gamble`* to follow my advice as I don't work at FAAANG or any other product-based company. In fact, I am jobless, *`I don't have 2000+ ratings also.`*
-   But seeing my leetcode profile might convince you to read this post at least once. Please share this post in your network if you found it useful, let's get started now.

Prologue
========

Lets's divide the whole lifecycle of learning DSA and Problem solving into 4 phases,

1.  Phase - 1(Super Saiyan 1) (*`You know a programming language but never touched DSA or never did problem-solving in the past`*)
2.  Phase - 2(Super Saiyan 2) (*`You know basic data structures and have done some ~200-250 problems on leetcode from different topics and different difficulty levels but not started with advanced data structures`*)
3.  Phase - 3(Super Saiyan 3) (*`You know basic and advanced data structures but you still struggling to perform better on leetcode contests especially with the hard problems, in other words, you are not feeling confident in DSA`*)
4.  Phase - 4(Autonomous Ultra Instinct) (*`You are not struggling with any topics, you have already mastered the art of problem-solving by brute practice, effort, and hard work`*)

Every leetcoder is definitely in one of the phases mentioned above, Let's tackle each of the Phases one by one... Also in the end I will share a **good way** to solve any problem on leetcode, along with getting the most out of it.

Phase - 1
=========

Leetcoders in this phase are just starting with problem-solving and data structures, they have never done any problem-solving in past. There are few goals of this phase,

1.  Getting familiar with the online problem-solving platforms, knowing how to write a code in your preferred programming language that is acceptable by online judges i.e., *`getting either AC, TLE, or WA in each problem you try to solve.`*
2.  Able to read and understand the problem statement, constraints, input, and output format of the problem.
3.  Able to convert the thinking into code and is comfortable with solving Easy level problems on basic Data structures and Algorithms.

FAQs in this phase
------------------

1.  What are the topics that come under Basic DSA? And in which order should I practice these topics?

    -   Here are the topics and the order one should practice Basic DSA,
        1.  Arrays
        2.  Strings
        3.  Matrix
        4.  Maths
        5.  Stack
        6.  Queue
        7.  Recursion
        8.  Searching and Sorting
        9.  Linked List
        10. Binary Trees and Binary Search Trees
        11. Asymptotic analysis (Big-O notation)
2.  Are there any good resources to study these topics from?

    -   Just type the topic name on google and learn from there only. Youtube also has good video lectures to follow.
3.  Which problems should I practice more in this phase, Easy, Medium, or Hard?

    -   Only solve Easy problems in this phase, no need to touch medium or hard problems. Do some 25-30 easy problems from each topic mentioned above and move on to the next topic. Sort the easy problems in order of increasing difficulty. This method of practicing problems is also called the BFS way of practicing.

-   *Any tips that you can think might be beneficial in this phase, do share in the comments, I will add them in the post along with your name.*

Phase - 2
=========

Now that you are comfortable with Basic DSA and able to implement most of the logic you are thinking in the programming language of your choice, its time to change the strategy and goals,

The goals of this phase are as follows,

1.  Practising more and more medium problems instead of practicing easy problems. Remember the below learning ratio that you will be getting from solving Easy, Medium, and Hard problems, *`so choose wisely.`*

    -   Approximately, Learning from 100 Easy Problems = Learning from 50 Medium problems = Learning from 25 Hard problems, *if picked wisely from the pool of problems we have on leetcode*.
    -   Since the learning is different in each difficulty level, it doesn't mean you can skip Easy or Medium problems and directly jump to hard problems.
    -   Go step by step. Consider 3 ladders in this journey,
        1.  Ladder - 1 (*`You have already climbed this ladder in phase-1`*)
        2.  Ladder - 2 (*`You are climbing this ladder in phase-2`*)
        3.  Ladder - 3 (*`You will be climbing this ladder in phase-3`*)
2.  Attending every single contest on leetcode. Leetcode conducts weekly and biweekly contests(*`both are 1.5hrs long`*) regularly. Remember, only attending the contest is not enough, analysing your performance, weak topics, and what went wrong comes in the phase too.

3.  I want to see you more confident in DSA than try to attend virtual contests on leetcode too. You can attend 2 or 3 virtual contests per week, depending on your schedule. This step is optional.

FAQs in this phase
------------------

1.  Which difficulty level should I practice more in this phase? Easy, Medium, or Hard?

    -   Do only Medium and Hard problems in this phase, also if you like to solve easy problems for fun then solve only those easy problems having less than 50% accuracy.
    -   Keep ratio like this 3:1 (Medium: Hard)
2.  In this phase too, do I need to practice in a BFS manner?

    -   Yes, again sort the problems in increasing order of difficulty and start solving medium problems. Do some 25-30 medium problems and 10-15 hard problems and move to the next topic.
3.  I am Unable to solve problems at this difficulty level? What should I do?

    -   At the end of this post, there is a method to practice problems, follow that.
4.  Can you suggest some topics that I should practice in this phase?

    -   Here is the list of topics one should practice in this phase, there is no specific order. You can do as you please...
        1.  Medium hard problems on topics mentioned in phase-1
        2.  Bit Manipulation and Bitmask
        3.  Two pointers
        4.  Sliding window
        5.  Hashing and Hash table
        6.  Divide and Conquer
        7.  Number theory
        8.  Monotonic stack
        9.  Advanced recursion and Backtracking (*Standard problems*)
        10. Greedy Algorithms (*Standard problems*)
        11. Simulation and observation-based problems
        12. Dynamic programming (*Standard problems*)
        13. Graph (*Standard problems*)

*This will probably be the longest phase in your learning, you might take 4-6 months to complete all of these topics. Depending on your speed. I may have missed some topics here, you can always add those in the comments.*

Phase - 3
=========

Congratulations,you have made it this far. Your hard work, efforts, and consistency are commendable. Now it's time to work more hard on Medium, Hard problems.

You should be focusing on advanced topics like DP, Graph, Rolling hash, String matching, etc. Leetcoders in this phase already knows what their week topics are. The only way to get better is to solve more and more problems that make you uncomfortable. In my opinion, do more and more hard problems in this phase from all possible topics on which you have done easy and medium questions. There are no specific goals in this phase, the only goal is to practice questions out of your league.

Phase - 4
=========

You have shattered your limits and now you are on a truly different level, your words are wisdom to people who are just starting with leetcode. No advice I can give to people in this phase, they are already doing a great job and can guide other people to achieve the same what they have achieved.\
Leetcoders in this phase either get their dream job or keep attending contests for fun. They don't do brute practice anymore. Reaching this state is no joke, and leetcoders who have made it this far are a true gem.

Consistency is the Key!
=======================

-   One of the major reasons people not improving in problem-solving and DSA is they are lacking consistency. It's hard to do leetcode daily, but if you convince your mind to do it as a habit then it will be easy.
-   *Let me link it with an example*, you do brush your teeth daily without even thinking twice. No matter what happens, you will brush your teeth because you have been doing it for a long time and you have no trouble doing it. Make the same habit with leetcode, fix a time slot in the day, and do Leetcode daily at the same time. If you do this 2 - 3 months without missing a single day, missing a day will be more difficult than doing leetcode that day.

How to Practise a Problem?
==========================

Let me share my way of practicing problems...

-   Pick a problem, don't see topic tags yet. Give 40 mins at least to the problem. Two things might happen after 40 mins, either you have got an idea of how to solve this problem or you have no clue what to do with the problem.

-   If you have an idea of how to solve the problem, go ahead and try to implement it. Try to get either TLE or WA or AC. If you have no idea how to solve the problem then open the question tags, think in that direction, and give some 20-30 mins.

-   After all of this struggle, either you have solved the problem or you are still clueless. Now the real learning begins, even if you have solved the problem follow the steps listed below,

    -   Open the discuss tab, and sort the posts by the number of votes. You will find some posts which contain only code and some posts with an explanation of the solution approach also.
    -   Read the post with the explanation of the solution approach, have a pen and paper alongside you. Draw test cases and try to understand the approach. Make your test cases and see whether this approach is working or not.
    -   Now you have a clear idea of the solution approach, try to implement it on your own. Don't copy the code from anywhere, you have to write your working code, it is crucial to write your code.
    -   Once you have got your solution accepted by this approach also look for different approaches in the discussion tab and do the same.
-   The Job isn't over yet, in some problems you will find a solution tab which is locked in some problems or unlocked in some problems. If the solution tab is unlocked then read the whole article, it's a gold mine just like the discussion tab.

*`You can always add anything extra here that works for you and can also share the same in comments so that it can help others as well.`*

How to remember previously solved problems?
===========================================

I have faced a problem after 2-3 months of starting leetcode. I was unable to remember how I solved a problem 2 weeks ago... I a sure a lot of people face this problem. Here is what I did to overcome this,

1.  Let's suppose I am currently solving problems on Binary Search. I created a notepad named BinarySearch.txt. If I am unable to reach the optimal solution to any problem then I will add a short explanation about the problem and all of the approaches in that notepad. I will add the most optimal code in that notepad too.
2.  The files like this keep increasing as you solve more and more topics, to handle all of this I created a GitHub repository where I am adding new questions daily that I am unable to solve and found interesting.
3.  Every morning, I wake up and take a quick look at the repository. It hardly takes 25-30 mins. In this way, I can remember the optimal approach to solve any problem which I have previously solved, and also I have started to recognize the pattern in problems.

That's it for this article, please don't mind my grammer mistakes. Thanks a ton for reading.

`I wanted the reward and not the struggle. I wanted the result and not the process. I was in love with not the fight but only the victory, and that's not how life works......`

How to get started with DSA and practice Leetcode Efficiently | by devdad

TOPICS WHICH YOU CAN'T SKIP | INTERVIEW PREPARATION | STUDY PLAN USING LEETCODE

### What is OBJECT-ORIENTED PROGRAMMING?

![](https://media.geeksforgeeks.org/wp-content/cdn-uploads/20190717114649/Object-Oriented-Programming-Concepts.jpg)

Object-oriented programming is a programming paradigm built on the concept of objects.\
In Other Words, it is an approach to problem-solving where all computations are carried out using objects.

1.  Program is divided into small parts called objects.
2.  Object-oriented programming follows a bottom-up approach.
3.  Have access specifiers like private, public, protected, etc.
4.  Adding new data and functions is easy.
5.  Provides data hiding so it is more secure than procedural programming.
6.  Overloading is possible in object-oriented programming.
7.  Data is more important than function.
8.  Provides the ability to simulate real-world
9.  Examples: C++, Java, Python, C#, JavaScript, Ruby, PHP, [VB.NET](http://vb.net/)

### TERMINOLOGIES

-   Class - A class is a group of objects that share common properties and behavior. It is a blueprint or template from which objects are created.

-   Object- Object is any real-world entity that can have some characteristics or which can perform some tasks. It is also called the instance of a class

For example, we can consider a car as a class that has characteristics like steering wheels, seats, brakes, etc.\
Class - color\
Red - an object of color

-   Constructor - Constructors are special methods whose name is the same as the class name. The constructors serve the special purpose of initializing the objects.

-   Interface - Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract.

-   Default constructor - The default constructor is the constructor which doesn't take any argument. It has no parameters.

-   Parameterized constructor - The constructors that take some arguments are known as parameterized constructors.

-   Copy constructor - A copy constructor is a member function that initializes an object using another object of the same class.

-   Friend Function - It is basically a function that is used to access all private and protected members of classes.

-   Member Function - It is basically a function that can be declared as members of a class. It is usually declared inside the class definition and works on data members of the same class.

-   Destructor - It frees up the resources and memory occupied by an object. Destructors are automatically called when an object is being destroyed.

-   Subclass - The subclass is a part of Inheritance. The subclass is an entity, which inherits from another class. It is also known as the child class.

-   Superclass - Superclass is also a part of Inheritance. The superclass is an entity, which allows subclasses or child classes to inherit from itself.

-   Abstract Class - An abstract class is a special class containing abstract methods. The significance of abstract class is that the abstract methods inside it are not implemented and only declared. So as a result, when a subclass inherits the abstract class and needs to use its abstract methods, they need to define and implement them.

-   Abstract Method - An abstract method is a method that doesn't have anybody.

-   Methods - A method is a procedure or function in OOPs Concepts. It is a set of instructions that are associated with an object.

-   Static Method - A static method is a method that belongs to a class, but it does not belong to an instance of that class and this method can be called without the instance or object of that class. Non-static methods can access any static method and static variable, without creating an instance of the object.

-   Overloading - Overloading is a compile-time polymorphism feature in which an entity has multiple implementations with the same name.

-   Overriding - Whereas Overriding is a runtime polymorphism feature in which an entity has the same name, but its implementation changes during execution.

-   Exception - An exception can be considered as a special event, which is raised during the execution of a program at runtime, that brings the execution to a halt.

-   Exception handling - It is the mechanism for identifying the undesirable states that the program can reach and specifying the desirable outcomes of such states.\
    Try-catch is the most common method used for handling exceptions in the program.

-   Garbage Collection - It refers to the mechanism of handling the memory in the program. Through garbage collection, the unwanted memory is freed up by removing the objects that are no longer needed.

-   Interface v/s Abstract class difference - Interface and abstract classes both are special types of classes that contain only the method declaration and not their implementation. But the interface is entirely different from an abstract class. The main difference between the two is that, when an interface is implemented, the subclass must define all its methods and provide its implementation. Whereas when an abstract class is inherited, the subclass does not need to provide the definition of its abstract method, until and unless the subclass is using it.\
    Also, an abstract class can contain abstract methods as well as non-abstract methods

-   Private - The access level of a private modifier is only within the class. It cannot be accessed from outside the class.

-   Default - The access level of a default modifier is only within the package. It cannot be accessed from outside the package. If you do not specify any access level, it will be the default.

-   Protected - The access level of a protected modifier is within the package and outside the package through child class. If you do not make the child class, it cannot be accessed from outside the package.

-   Public - The access level of a public modifier is everywhere. It can be accessed from within the class, outside the class, within the package and outside the package.

### Why we use object-oriented programming?

Object-oriented programming is the programming paradigm that is defined using objects. Objects can be considered as real-world instances of entities like class, that have some characteristics and behaviors.

-   OOPs helps users to understand the software easily, although they don't know the actual implementation.
-   With OOPs, the readability, understandability, and maintainability of the code increases multifold.
-   Even very big software can be easily written and managed easily using OOPs.

### What are the main features of OOPs?

### Data Abstraction

1.  Data abstraction refers to providing only essential information about the data to the outside world, hiding the background details or implementation.
2.  Hiding the implementation and displaying only the functionality to the users.

#### Advantages

1.  It reduces the complexity of viewing things.
2.  Reduces the duplication of the code

#### Real Life Example

Consider a real-life example of a man driving a car. The man only knows that pressing the accelerators will increase the speed of the car or applying brakes will stop the car but he does not know about how on pressing the accelerator the speed is actually increasing, he does not know about the inner mechanism of the car or the implementation of the accelerator, brakes, etc in the car.

### Encapsulation

It describes the idea of bundling data and methods that work on that data within one unit.

#### Advantages

1.  Encapsulation protects an object from unwanted access by clients.
2.  Simplifies the maintenance of the application

#### Real Life Example

A Real-Life Example of Encapsulation is a School Bag.

### Polymorphism

The word polymorphism means having many forms. It describes the concept that different classes can be used with the same interface.\
Polymorphism is the ability of any data to be processed in more than one form.

Polymorphism is divided into two types:

-   Compile Time Polymorphism - Compile time polymorphism, also known as Static Polymorphism, refers to the type of Polymorphism that happens at compile time. What it means is that the compiler decides what shape or value has to be taken by the entity in the picture.

-   Runtime Polymorphism - Runtime polymorphism, also known as Dynamic Polymorphism, refers to the type of Polymorphism that happens at the run time. What it means is it can't be decided by the compiler. Therefore what shape or value has to be taken depends upon the execution. Hence the name Runtime Polymorphism.

#### Advantages

1.  It helps the programmer to reuse the codes, i.e. classes once written, tested and implemented can be reused as required. Saves a lot of time.
2.  A single variable can be used to store multiple data types.

#### Real Life Example

Like a man at the same time is a father, a husband, an employee. So the same person possesses different behavior in different situations. This is called polymorphism.

### Inheritance

Inheritance is a feature of OOPs which allows subclasses classes to inherit properties from the parent class.

Types of Inheritance

-   Single inheritance - When a class inherits from a single class, it is known as a single inheritance

-   Multiple inheritances - Multiple inheritances come into the picture when a class inherits from more than one base class.

    Parent 1 && Parent2 → child

-   Multilevel inheritance - When there is a chain of inheritance, it is known as multilevel inheritance.

    Example: Animal → Dog → Puppy\
    Puppy Inherits from the Dog Class, Dog class inherits from the Class Animal.

-   Hierarchical inheritance - When two or more classes inherit a single class, it is known as hierarchical inheritance.

    Example: Animal → Dog = Cats

-   Hybrid inheritance - Hybrid inheritance is a combination of multiple and multi-level inheritances.

#### Advantages

The main advantages of inheritance are code reusability and readability. When a child class inherits the properties and functionality of the parent class, we need not to write the same code again in the child class. This makes it easier to reuse the code, makes us write less code and the code becomes much more readable.

#### Real Life Example

If there is a class such as 'vehicle', other classes like 'car', 'bike', etc can inherit common properties from the vehicle class.

### What is Overloading and Overriding?

When two or more methods in the same class have the same name but different parameters, it's called Overloading.

When the method name and parameters are the same in the superclass and the child class, it's called Overriding.


### Code Examples

### Data Abstraction

JavaScript is a weakly typed language and does not have the classical built-in support for abstraction like OOP languages. Instead, JavaScript has the capability to support OOP, and thus can achieve OOP functionalities, which is known as Object Oriented JavaScript (OOJS). Data abstraction can be achieved by inheritance and composition.

In JavaScript, prototypes and closures can help us accomplish data abstraction.

```

function Employee(name, age, baseSalary) {
    this.name = name;
    this.age = age;
    this.baseSalary = baseSalary

    let monthlyBonus = 1000;

    // This is not exposed to the user
    let calculateMonthlyBonus = function () {
        let finalSalary = baseSalary + monthlyBonus
        console.log("Final Salary is : ", finalSalary)
    }

    this.getEmpDetails = function () {
        console.log("Name: " + this.name,
            "Age: " + this.age,
            "baseSalary: " + this.baseSalary)
    }
    calculateMonthlyBonus()
}

let emp1 = new Employee("John", 30, 2000);
emp1.getEmpDetails()

OUTPUT : Final Salary is :  3000
Name: John Age: 30 baseSalary: 2000

```

### Encapsulation

It describes the idea of bundling data and methods that work on that data within one unit.

```

class Employee {
    setEmpDetails(name, id, phone) {
        this.name = name;
        this.id = id;
        this.phone = phone;
    }

    getEmpName() {
        console.log(this.name);
    }
    getEmpId() {
        console.log(this.id);
    }
    getEmpPhoneNo() {
        console.log(this.phone);
    }
}

let emp1 = new Employee()
emp1.setEmpDetails("John", 319, 9788786086)
emp1.getEmpName();

OUTPUT : John

```

### Polymerphism

It is the ability to create a variable , a function or an object that has more than one form.

```

class Animal{

    constructor(name){
        this.name = name;
    }

    eats(){
        console.log(this.name, "eat food")
    }
}

class Alligator extends Animal{

    eats(){
        console.log(this.name, "eat fishes")
    }
}

let murphy = new Alligator("Murphy");
murphy.eats()

OUTPUT : Murphy eats fishes

```

### Inheritance

```

class Car {
    setName(name) {
        this.name = name;
    }

    startEngine() {
        console.log("Engine started For " + this.name);
    }
    stopEngine() {
        console.log("Engine stopped For " + this.name);
    }
}

class Toyota extends Car {

    topSpeed(speed) {
        console.log("Top Speed For " + this.name + " is " + speed);
    }
}

let myCar = new Toyota();
myCar.setName("Camry");
myCar.startEngine()
myCar.stopEngine()
myCar.topSpeed(200)

OUTPUT :
Engine started For Camry
Engine stopped For Camry
Top Speed For Camry is 200
```

Complete OOPS Guide | Interview Prepration | Freshers

🎯**TCS Off Campus Drive 2022**

Apply Link: [https://jobforfresher.in/tata-consultancy-services-hiring-2022/](https://jobforfresher.in/tata-consultancy-services-hiring-2022/)

🎯** Capgemini Off Campus Drive 2022** 

Apply Link: [https://alljobsinindia.in/capgemini-off-campus-drive-2022/](https://alljobsinindia.in/capgemini-off-campus-drive-2022/)

🎯**Wipro Off Campus Drive 2022**

Apply Link: [https://jobforfresher.in/wipro-off-campus-2022-for-project-engineer-apply-now/](https://jobforfresher.in/wipro-off-campus-2022-for-project-engineer-apply-now/)

🎯 **Cloud Mayo Off Campus Drive**

Apply Link: [https://alljobsinindia.in/cloudmoyo-off-campus-hiring/](https://alljobsinindia.in/cloudmoyo-off-campus-hiring/)

🎯**Zycus Off Campus Drive 2022**

Apply Link: [https://jobforfreshar.in/index.php/zycus-off-campus-2022/](https://jobforfreshar.in/index.php/zycus-off-campus-2022/)


🎯**Meesho Is Hiring Business Analyst**

Apply Link: [https://alljobsinindia.in/meesho-is-hiring-business-analyst/](https://alljobsinindia.in/meesho-is-hiring-business-analyst/)


🎯**Zoho is hiring Frontend Developer**

Apply Link: [https://alljobsinindia.in/zoho-is-hiring-frontend-developer/](https://alljobsinindia.in/zoho-is-hiring-frontend-developer/)

Meesho, Zoho, Wipro and more. | Job Opportunities | Apply Now!

I extensively researched about companies hiring internationally which support visa & relocation for SDE1/2 and above. So sharing list of companies with all of you:

**London**

- Google
- Amazon
- Apple
- Meta
- Bloomberg
- Spotify
- SnapChat
- Bytedance
- Yelp
- Vercel
- Bulb
- Mobiquity
- Expensify
- Free Now
- EF Education First
- Canva
- Intercom
- Curve
- The Lego group
- Plaid
- Transferwise
- Palantir Technologies
- Algolia
- Revolut
- PayFit
- SumUp
- Trainline
- Deliveroo
- Collibra
- Hashicorp

**Berlin, Germany**

- Amazon
- Zalando
- Ubisoft
- Klarna
- Delivery Hero
- Adnymics
- Hive.app
- N26
- Signavio
- Wayfair
- Free Now
- Trivago
- Babbel
- Personio
- RapidAPI
- HelloFresh
- PayFit
- SumUp
- Taxfix
- Blinkist
- SoundCloud
- Pitch
- Qonto
- Gorillas
- Hashicorp
- Project44
- TradeRepublic
- Immobilienscout24
- Clark
- Forto
- Raisin
- InVision
- Tipico
- Container xChange
- Sunday
- Celus
- Navvis
- e-Bot7
- Bigpoint

**Amsterdam, Netherlands**

- Databricks
- Uber
- Optiver
- Vercel
- Booking.com
- Mobiquity
- Miro
- Plaid
- SumUp
- Gorillas
- Hashicorp

**Dublin**

- Microsoft
- Amazon
- Vercel
- Verizon Connect
- Free Now
- Intercom
- Meta
- SquareSpace
- DataDog
- Luxembourg

FAQs❓

Q: Do we require to do masters/MS to work there?
A: No, most of these companies will provide visa & relocation.

Q: Does getting international job makes me more financially stable?
A: No, there are tons of better opportunities in India as well which pay huge these days. So decide accordingly.

Q: From where did you collected the above information?
A: LinkedIn posts of people joining XYZ company, companies mentioning in their job descriptions explicitly that they sponsor visa, India to EU Discord server, Shubheksha GitHub's repo.

Q: Can interns apply to international internships as well?
A: Most companies do not sponsor visa for interns, but some companies like Meta does for intern postions as well.

Q: Is interview process similar as compared to India?
A: Yes, the process is exactly similar.

Q. Do I need to upvote this post?
A: Ye bhi koi puchne ke baat hai :)

Feel free to comment down other companies with whom you interviewed!

International Hiring for SDEs in India | International Offer Companies | VISA included | SDE-1,2,3 | by devdad

I continue to see posts here complaining about finding good women. I’ll explain to you what they key is in sausage fest tech metros.

![](https://i.scdn.co/image/ab67616d0000b2734e6ab1cb432cc722b0ec91e8)

I will assume you are the stereotype Sigma Male SWE that works all day, hits the gym (if you don’t, that’s a minimum requirement), then does some sort of “studying” or whatever after.

Dating in tech Metros is hard. You might think that most women are extremely leftist / child free / abolitionist colored hair people. The truth is, these people are the most desperate and most available because they are the least desirable. There are normal women to choose from, many great female friends in SF tell me they can’t find anyone good to date.

Generally, the normal ones are taken, don’t want to date software engineers due to bad experiences in the past, or can be found only via friend groups because they were burned 1 too many times on dating apps. I’m grateful I’m engaged to a great person. My fiancé has repeatedly said that if she hadn’t dating me she’d be filtering out SWEs on dating apps too.

I think part of the reason you might find dating hard is because of the “bro-y” lifestyle SWE dudes live. Hustle culture, move here for a job and make no community connections, no hobbies / SWE stereotype hobbies like Rock Climbing, profile pic is the guy in sunglasses, slim profile with a little bit of muscle, etc. The biggest one though is SWEs can’t talk about anything but tech, politics, and money, and the best women do not care about that. They care about people, family, and hobbies.

So here are a few tips:

- Make friends with the kind of people you’d be compatible with. The friend group can’t be a sausage fest. Women will come.

- Become a part of your community. Volunteer for example, you’ll get to know many great people. The women will be normal.
 
- Get a hobby that isn’t some boring stereotype. “Oh you do rock climbing and gym?? Wow I’ve heard that from every other tech guy this week.” Hobby = interesting, interesting = relationship. Try archery, shooting, woodworking, etc. It’s something to talk about that isn’t tech, and you can meet good women via many hobbies.

- Don’t talk about finance or politics around women. Touch on tech briefly to explain your job / passion and that’s it. The best women I’ve met care much more about relationships, friends, family, and hobbies. They will be interested in you if you can hold an hour long conversation and focus on people.
 
- Your looks honestly don’t matter that much. Just be healthy, don’t be too overweight, shave or groom your facial hair well, and be clean / smell good. Don’t have greasy hair. The bar for men is very low, all of the above are dirt easy to do.

- Your race does matter, in spite of what people tell you. White women prefer white men, for example.

- Oh, and don’t wear those cringy tech shirts. Get some brand-less clothes and some nice well-fitting clothes for dates. Ask a female, gay, or well-dressed friend if you really need help here.
 
- for the love of god, don’t blab about your startup / startups for the entire date. Women DO NOT care that much. Passion is very attractive, but only to a point.
 
- Be ready to settle down, and prioritize your relationship over work. Great women will be able to feel out whether or not you’re going to prioritize them—“founder” is a big 🚩🚩
 
- Don’t flash your money unless you want to attract people who just date you for the money.
 
- If you must do dating apps, don’t put SWE in your profile, add pictures of you with friends (preferably mixed gender), avoid sunglasses pics, and be well groomed / dress well. Hobby pics are ok too.
 
- The women that want to fuck on the first few dates are often the worst ones to date. Don’t go into a date looking for sex, look for a relationship. The sex will come.
 
- De-techify your apartment / room. One person I know has pictures of inspiring people on the wall, including Bezos & Musk. Women will see that & run. Move your office out of your bedroom if you have the space.

Thank you for coming to my Ted talk!

Dating in Software Engineering World by devdad | Blogs and Jobs

Software Development Job Openings for the day 👇🏻
[Ola, Grab, Postman, and Samsung]

**Ola**
Software Development Engineer I
Link: [Apply Now](https://career10.successfactors.com/career?career_ns=job_listing&company=anitechnol&rcm_site_locale=en_GB&career_job_req_id=69721&jobPipeline=workattech&utm_source=workattech)

**Grab**
Software Engineer I
Link: [Apply Now](https://grab.wd3.myworkdayjobs.com/en-US/Careers/job/Bangalore-Salarpuria-Adonis/Software-Engineer--Fullstack_R-2022-4-0189?source=workattech)

**Postman**
Software Engineer I
Link: [Apply Now](https://boards.greenhouse.io/postman/jobs/5095264003?gh_src=7ad26f843us&s=workattech&source=workattech)

**Samsung**
Fullstack Developer
Link: [Apply Now](https://www.linkedin.com/jobs/view/3044615496/?source=workattech)

For more such job updates,keep visiting [devdad](www.devdad.org).

Software Development Job Openings for the day 👇🏻 [Ola, Grab, Postman, and Samsung]

Software Development Job Openings for the day 👇🏻
[BookMyShow, ClearTax, Amazon, and Cohesity and more]

**BookMyShow**
Software Development Engineer
Link: [https://bit.ly/3vT3GZr
](https://in.bookmyshow.com/careers/job-view/software-development-engineer-fullstack-technologies/?id=mp02utu&source=workattech)

**Amazon**
SDE Intern
Link: [https://bit.ly/37X7IrN](https://www.amazon.jobs/en/jobs/2043520/software-development-engineer-intern?source=workattech)

**ClearTax**
Frontend Engineer
Link: [https://bit.ly/3s4J0fM](https://cleartax-talent.freshteam.com/jobs/_R__5gfyHJgj/frontend-2?source=workattech)

**Cohesity**
Senior Software Engineer
Link: [https://bit.ly/3MZApTZ](https://www.linkedin.com/jobs/view/3051710127/?source=workattech)

**Flipkart**
Software Developer
Link: [https://bit.ly/371Eis5](https://www.linkedin.com/jobs/view/2764364949/?source=workattech)

**Flock**
Frontend Engineer
Link: [https://bit.ly/37PiMr1](https://careers.flock.com/job-description.html#ecd6edbf-4ca1-4149-9b8d-3cae3293b381?source=workattech)

**PayU**
Software Engineer
Link: [https://bit.ly/3Kvxcd3](https://jobs.eu.lever.co/payu/baf9c742-5119-4334-bc7e-7c4d033286ed?lever-source=workattech)

**Paytm**
Software Developer
Link: [https://bit.ly/3vTkD62](https://jobs.lever.co/paytm/ad4d1e36-153c-419c-a0e8-8c7341f26f39?lever-source=workattech)

Software Development Job Openings | BookMyShow,Amazon,Flipkart and more | Apply Now

**IBM is Hiring | 🎖2022 batch**
BE ME BSc MSc BCA MCA Diploma

[https://careers.ibm.com/job/15401907/associate-technical-engineer-remote](https://careers.ibm.com/job/15401907/associate-technical-engineer-remote)


**Amazon Hiring SDE-I**

🎖Batch - 2019/20/21
[https://amazon.jobs/en/jobs/1991382/sde-i](https://amazon.jobs/en/jobs/1991382/sde-i)


**Bitwise Drive | 🎖2022 Batch**

CTC - 💰4LPA
[https://bit.ly/37nD5eM](https://bit.ly/37nD5eM)

**Adobe | 🎖2021 batch | 💰24LPA**

[https://firstnaukri.com/careers/customised/landingpage/adobe/13122021/index.html](https://firstnaukri.com/careers/customised/landingpage/adobe/13122021/index.html)

**MyAnatomy | Full Stack Developer**

🎖 Batch - 2018 to 2022
💰 CTC - 5lpa to 7lpa
📝[https://bit.ly/3L6s2oT](https://bit.ly/3L6s2oT)

**Capgemini Drive | 🎖2019-21 Batch**

✅ Eligible - BE ME MCA MSc
🧑🏻‍🦰 Female Candidates
💰 CTC - 3Lpa

[capgemini.com/in-en/capgemini-exceller-diversity-off-campus-drive-for-2019-2020-2021-graduates](https://capgemini.com/in-en/capgemini-exceller-diversity-off-campus-drive-for-2019-2020-2021-graduates)

Amazon | IBM | Adobe and more | Job Opportunities | 4 to 24 LPA | Freshers

**Zoho is Hiring**

Role: Software Developer

Specialization: Any

Eperience: 0 to 2 years

Apply: [https://bit.ly/3JJu10R](https://bit.ly/3JJu10R)

Job Location: Across India 


**Salesforce is Hiring**

Role: Associate Member of Technical Staff 

Qualifications: BE/B.Tech

Specialization: CS, IT or related domains of circuit branches

Experience: Freshers

Batch: 2022

Percentage Criteria: CGPA of 7 or above, with no active backlogs

Apply: [https://bit.ly/3M7mI4K](https://bit.ly/3M7mI4K)

Location: Bangalore, Hyderabad

Salesforce and Zoho Hiring | Freshers | Job Opportunities

**Amazon is Hiring**
 
Role: SDE I 
  
Education: Bachelor’s degree or higher
  
Branch: Computer Science or related discipline
  
Batch: 2019, 2020 or 2021

Apply (Bengaluru): [https://bit.ly/3EyWbLg](https://bit.ly/3EyWbLg)

Apply (Hyderabad): [https://bit.ly/3jUOzsN](https://bit.ly/3jUOzsN)

Apply (Chennai): [https://bit.ly/3jXdSue](https://bit.ly/3jXdSue)

Apply (Gurgaon): [https://bit.ly/3jUNEZC](https://bit.ly/3jUNEZC)

For more such job updates,Follow devdad on linkedin:

[**devdad tech**](https://www.linkedin.com/in/devdad-tech-9a8b32231/)

Amazon Hiring Multiple Locations | Freshers | PAN India

**GlobalLogic is Hiring** 

Qualifications: B.Tech /B.E / M.Tech/MCA

Branch: CSE, IT, ECE and aligned Branches

Experience: Fresher's to 1 Year

Batch: 2020/21 Passout

Percentage Criteria: 60% or more starting from 10th until degree

CTC: 4.74 LPA

Apply:[https://bit.ly/3728e7k](https://bit.ly/3728e7k)
 
Job Location: Bangalore


**Wipro NTH [Elite National Talent hunt]**

Qualifications: BE/BTech/ME/MTech

Branch: All branches

Batch: 2021, 2022

Percentage Criteria: 60% or more starting from 10th until degree

CTC: 3.5 LPA

Apply: [https://bit.ly/3J3PbIb](https://bit.ly/3J3PbIb)
 
Last date to register: May 22, 2022

One backlog is allowed till the Offer stage

GlobalLogic and WIPRO Hiring | Freshers | Jobs and Opportunities

**CDK Global @ Hiring | 2021 Batch
💰4.5LPA**

Apply Link- [bit.ly/3sZbeYG](https://bit.ly/3sZbeYG)

**BirlaSoft Hiring Application Developer | 2022 Batch**

[firstnaukri.com/careers/customised/landingpage/birlasoft/2492020/index.html#job_details](https://firstnaukri.com/careers/customised/landingpage/birlasoft/2492020/index.html#job_details)


**Wonderbiz Is Hiring | CS/IT 2022 Batch**

[https://www.firstnaukri.com/careers/customised/landingpage/wonderbiz/index.html](https://www.firstnaukri.com/careers/customised/landingpage/wonderbiz/index.htm)


**Microsoft is Hiring | Software Engineering | 2022 Batch**

[https://careers.microsoft.com/students/us/en/job/1062742/Software-Engineer-Full-Time-Opportunity-Engage](https://careers.microsoft.com/students/us/en/job/1062742/Software-Engineer-Full-Time-Opportunity-Engage)
  

**MedPlus is Hiring | Software Role | 2019 - 2021 Batch | 
💰5.5LPA**
  
[https://itcareers.medplusindia.com/job-openings](https://itcareers.medplusindia.com/job-openings) 


**Cornerstone Hiring Associate Engineer | B.Tech | 2020-21 Batch**

Link to apply: [https://cornerstone.csod.com/ux/ats/careersite/2/home?c=cornerstone&source=Indeed#/requisition/6677](https://cornerstone.csod.com/ux/ats/careersite/2/home?c=cornerstone&source=Indeed#/requisition/6677)
  

**JK Technosoft is Hiring | 2021 Batch | B.Tech, MCA**
💰 3.5 LPA

[https://bit.ly/3uySCj3](https://bit.ly/3uySCj3)


**Accenture is Hiring | Associate Software Engineering
💰 4.5LPA | 2019-21 Batch**
  
[https://indiacampus.accenture.com/register/accenture/ndirl1/apply/?event=3233](https://indiacampus.accenture.com/register/accenture/ndirl1/apply/?event=3233)


**DXC is Hiring | B.Tech CS/IT**

[https://bit.ly/3msRUjA](https://bit.ly/3msRUjA)

**Cognizant Hiring GenC Developer [Off Campus] | 2019 2020 2021 Batch 
💰4LPA**

[app.joinsuperset.com/join/#/signup/student/jobprofiles/cb1b75ce-18ba-4a7f-99c3-b9a35a1dc80f](https://app.joinsuperset.com/join/#/signup/student/jobprofiles/cb1b75ce-18ba-4a7f-99c3-b9a35a1dc80f)

**TetraSoft Off Campus | BE MCA | 2021 Batch
💰3.5 to 4.8LPA**

[firstnaukri.com/careers/customised/landingpage/tetrasoft/index.html](https://firstnaukri.com/careers/customised/landingpage/tetrasoft/index.html)

**Mindtree Off Campus Drive | 2020 & 2021 Batch
💰3LPA**

[mindtree.com/careers/campus-careers](https://mindtree.com/careers/campus-careers)

**VIRTUSA OFFCAMPUS DRIVE | 2020 - 2021 Batch
💰 5-10LPA**

[https://mycareer.virtusa.com/job/associate-consultant-technology-7/](https://mycareer.virtusa.com/job/associate-consultant-technology-7/)


**XPERI Off-Campus Drive | 2020 & 2021 Batch
💰8.2LPA**

[match.myanatomy.in/sc/617a5b19b87cd907825cf061/n](https://match.myanatomy.in/sc/617a5b19b87cd907825cf061/n)


**Zoho - Technical Support Engineer | 2019 - 2021 Batch**

[bit.ly/3H1bFbN
](https://bit.ly/3H1bFbN)

**Mindtree is Hiring | Software Engineer | 2021 & 2022 Batch
💰 4LPA**

Link to apply - [https://bit.ly/Apply-for-Mindtree](https://bit.ly/Apply-for-Mindtree)


**IBM Off Campus Drive | 2020 2021 Batch | BE B.Tech BCA BSc**

[https://careers.ibm.com/job/13801135/application-developer-java-full-stack-bangalore-in/
](https://careers.ibm.com/job/13801135/application-developer-java-full-stack-bangalore-in/
)

**Tech Mahindra Off Campus Drive | Batch - 2020 & 2021**

[registration.techmahindra.com/Candidate/RegDefault.aspx](https://registration.techmahindra.com/Candidate/RegDefault.aspx)


**Hexaware Off Campus 💰4LPA**

2021 Batch
[https://bit.ly/3kPtGjJ](https://bit.ly/3kPtGjJ)

2022 Batch
[https://bit.ly/3nxK5uT](https://bit.ly/3nxK5uT)


**Global Edge is Hiring | 🎖2020 & 2021 Batch
💰3.8LPA**
[
match.myanatomy.in/sc/619cdc4ea577a7118200cb87/n](https://match.myanatomy.in/sc/619cdc4ea577a7118200cb87/n)


**Zensar Hiring Junior Engineer  | 2020 & 2021 Batch
💰 4LPA**

[https://zensar.register.hiringtests.in/index.php?r=user/candidateIndex](https://https://zensar.register.hiringtests.in/index.php?r=user/candidateIndex)


**JMAN Off-Campus | 🎖2019 2020 2021 Batch | BE BSc MCA 
💰3.5LPA**

[https://bit.ly/3ldKgtC](https://bit.ly/3ldKgtC)


**LG Soft Off Campus | 2020 & 2021 Batch
💰6LPA**

[match.myanatomy.in/sc/61b0837fd665a819c351c10d/n](https://match.myanatomy.in/sc/61b0837fd665a819c351c10d/n)

Software Engineering Jobs | Freshers | 30th April 2022

```
Download Hotstar MOD Apk VIP Unlocked 2022
App Name	Hotstar Apk
Size	41MB / 14MB
Version	v12.5.0
Android Support	4.0 or above
Last Updated	3 April 2022
Developer. devdad
Price	FREE
Final Words
I hope you liked this Disney+ Hotstar MOD APK for Watching All Premium & VIP Hotstar Content for Free. Thank You For Visiting!
```

**Download Now:**

[Version 1
](https://www.ytricks.net/hotstar-apk/download/4/)

[Version 2](https://www.ytricks.net/hotstar-apk/download/3/)

[Version 3](https://www.ytricks.net/hotstar-apk/download/2)

[Version 4](https://www.ytricks.net/hotstar-apk/download/1)

Hotstar MOD apk Premium Unlocked | Free Download

![](data:image/png;base64,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)

Spring Boot is one of the most used backend framework in the world when it comes to scalable industry level applications.


![](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS-RFXJsf3XX35hbtEnj-MqM1W5oX0N0QWeOjhliYd-APhgYhnyRX2v0irpiQo0bCRU2BI&usqp=CAU)


**CRON** Job is also one of the most widely use case in application in order to handle concurrency and task scheduling and Spring boot makes it really easy for us to make **CRON** Jobs.

In this demo, we'll illustrate how the Spring @**Scheduled** annotation can be used to configure and schedule tasks.

The simple rules that we need to follow to annotate a method with @**Scheduled** are:

- the method should typically have a void return type (if not, the returned value will be ignored)
- the method should not expect any parameters

Now Firstly we will have to enable support for scheduling in our Spring Boot application:

```
@Configuration
@EnableScheduling
public class SpringConfig {
    ...
}
```

That's it.Now lets see how we can use and schedule **CRON** Jobs in different ways.

- **Schedule a Task at Fixed Delay**

```
@Scheduled(fixedDelay = 1000)
public void scheduleFixedDelayTask() {
    System.out.println(
      "Fixed delay task - " + System.currentTimeMillis() / 1000);
}
```

- **Schedule a Task at a Fixed Rate**

```
@Scheduled(fixedRate = 1000)
public void scheduleFixedRateTask() {
    System.out.println(
      "Fixed rate task - " + System.currentTimeMillis() / 1000);
}
```

- *Fixed Rate vs Fixed Delay*

> The fixedDelay property makes sure that there is a delay of n millisecond between the finish time of an execution of a task and the start time of the next execution of the task.

> The fixedRate property runs the scheduled task at every n millisecond. It doesn't check for any previous executions of the task.


- **Schedule a Task With Initial Delay**

```
@Scheduled(fixedDelay = 1000, initialDelay = 1000)
public void scheduleFixedRateWithInitialDelayTask() {
 
    long now = System.currentTimeMillis() / 1000;
    System.out.println(
      "Fixed rate task with one second initial delay - " + now);
}
```

*You can also use Cron Expressions to run your jobs.*

- **Schedule a Task Using Cron Expressions**

```
@Scheduled(cron = "0 15 10 15 * ?")
public void scheduleTaskUsingCronExpression() {
 
    long now = System.currentTimeMillis() / 1000;
    System.out.println(
      "schedule tasks using cron jobs - " + now);
}
```

*Now How to write CRON expressions is for some another time!!*

- **Parameterizing the Schedule**

Hardcoding these schedules is simple, but we usually need to be able to control the schedule without re-compiling and re-deploying the entire app.

We'll make use of Spring Expressions to externalize the configuration of the tasks, and we'll store these in properties files.

```
A fixedDelay task:

@Scheduled(fixedDelayString = "${fixedDelay.in.milliseconds}")

A fixedRate task:

@Scheduled(fixedRateString = "${fixedRate.in.milliseconds}")

A cron expression based task:

@Scheduled(cron = "${cron.expression}")

```

That's it for today's blog.
See you guys in the next one!

Running CRON Jobs in Spring boot Java the easy way | Spring Boot Tutorials

**Problem**:

```
Map<String, String> phoneBook = people.stream()
                                      .collect(toMap(Person::getName,
                                                     Person::getAddress));
```

I get java.lang.IllegalStateException: Duplicate key when a duplicated element is found.

Is it possible to ignore or handle such exception on adding values to the map?



**Solution:**

This is possible using the mergeFunction parameter of Collectors.toMap(keyMapper, valueMapper, mergeFunction):

```
Map<String, String> phoneBook = 
    people.stream()
          .collect(Collectors.toMap(
             Person::getName,
             Person::getAddress,
             (address1, address2) -> {
                 System.out.println("duplicate key found!");
                 return address1;
             }
          ));
```

mergeFunction is a function that operates on two values associated with the same key. ***adress1*** corresponds to the first address that was encountered when collecting elements and ***adress2*** corresponds to the second address encountered: this lambda just tells to keep the first address and ignores the second.

How to handle duplicates Keys when producing map using streams?

I will cover the most important topics asked in interviews cs core. Most important topics related to OS/DBMS/OOPS/CN.

CONTENT OF THIS POST :
Most important topics related to OS/DBMS/OOPS/CN.

**Important Topic for OS**

```
- Process (Attributes, state, life cycle, PCB) vs Thread.
- Scheduling Algorihtms
- Multiprogramming vs Multiprocessing vs Multitasking vs Multithreading.
- Memory Allocation
 a) Fixed Partioning
 b) Dynamic Partioning
 c) Paging
 d) Segmentation
- Internal and External Fragmentation.
- Memory Allocation Technique.
- Page replacement Algos
- Deadlock
- Critical section problem
- Mutex vs Semaphore
```

**Important Topic for DBMS**

```
- Advantage of DBMS
- All type of Keys
- Normalization
- SQL queries
- Relational Algebra
- Joins
- Trigger, cursor, view
- Dirty read problem
- Conflict serializable vs View serializable.
- ACID properties.
- Indexing | Indexing methods
```

**Important Topic for COMPUTER NETWORKS**

```
- Network Topology
- Switch hub router bridge
- Transmission modes
- ipv4 vs ipv6
- subnetting in IP
- OSI layer
- TCP/IP model
- TCP vs UDP
- DNS DHCP FTP HTTP vs HTTPS SMTP SNMP
- Flow vs Error control
```

**Important Topic for OOPS**

```
- Class and Objects.
- Feature/characteristics of OOPs.
- Compile time and Runtime polymorphism.
- Variable scopes.
- static (variables, Functions, Objects).
- Inheritence (Type and Mode)
- Virtual (Functions and Class)
- Abstract class and Interface.
- Friend function and Friend class.
- Call by value, refrence.
- This pointer
- Abstraction
- Exception Handling
- Constructor and Destructor.
- Copy constructor
- copy assignemnt operator
- Refrences variable
- Const (variable, Function, Arguement)
- Overloading (Function, Constructor, Operator)
- Function overriding and Inline function.
```
**Do Comment and suggest topics you want blogs on.**

The Ultimate CS Core Subjects Interview Guide | Crack any Product based Company

```
Education: BTech in Computer Science from Tier 1
Years of Experience: 2 years and 10 months
Prior Experience: SSE & Tech Lead at MNC
Company: Flipkart
Title/Level: SDE 2
Location: Bangalore
Previous Comp: 20 Lakh Fixed (includes PF)
Fixed Salary: 33 L
Variable Incentive pay: 3.3 L
Stock bonus: 12 Lakh stock grant vested over 4 years
Total comp (Salary + Bonus + Stock): ~40 L (first year)
```

```
Status: SSE & Tech lead, BTech CS from Tier 1
Position: SDE2 at Flipkart
Location: Bangalore, India

Got email on one day that there is a drive on next day (Saturday) with 4 rounds happening in a single day, with each round being elimination round.

Round 1 - Machine Coding Round [120 min]
Design a question-answer platform for developers. (Social media platform) where users can ask any tech related questions [Similar to stackoverflow].
Some features to build for example -
a) Signup, Signin , Session Handling etc.
b) Posting of questions, answers, comments.
c) Upvoting / Downvoting.
d) Subscribing to some topic / question / answer.
e) Some filtering based on the parameters passed. etc

One panelist will be assigned to you and will see the screen whole time while you code.
The code should have the minimum number of certain features implements. It should be working, extendable and scalable.

Round 2- DSA Round

Array of string is given ["abc, def, xyz, ..."]. You have to find the groups of related strings.
A String is related if the distance between each of the character of the string [at each index] is same.
Example - (d-a = 3 | e-b.= 3 | f-c=3) --> Hence abc and def are related.
https://leetcode.com/problems/maximum-swap/
Round 3 - LLD/HLD System Design Round

Design Bookmyshow.
Discussion on movement of flow between different models.
How can the seats be locked [Synchronisation and Mutex was expected].
Describe full User Search Flow and User Booking flow.

Had to write all the models to clear the round.

Round 4 - Hiring Manager Round

Why Change in company?
Current role in your organisation.
Describe HLD of your current or any project in the current organisation on which you have worked on.
Discussion on Microservices implementation.
a) What all microservices is there in your current project.
b) Describe the full flow of the process.
Some behavioural question on leading team and handling issues.
Hiring manager was quite kind and supportive. After all the question he described about the work that they do and what all can i expect in detail.

After 1.5 week got an email that they are going ahead with the candidature.
```

Flipkart | SDE2 | Bangalore | Feb 2022 [Offer] | Interview Experience and Compensation

```
Education: Btech in CS(tier -3 college)
Years of Experience: 3.9 years
Prior Experience: 2 product based companies
Date of the Offer: 02/03/2022
Company: Paypal
Title/Level: Software Engineer 2
Location: Bangalore
Salary: 25,00,00
Signing Bonus: 2L
Stock bonus: $21K vested over 3 years
Bonus: 2L
Total comp (Salary + Bonus + Stock): 34L approx per year
Benefits: standard paypal benefits
Team I will be working is Risk and Fraud detection in payments

Please help me some info in terms of career prospectives
```

PayPal | SDE-2 | Bangalore

```
Education: B.Tech from tier 2 college
Years of Experience: 7+
Current comp: ₹37,50,000
Date of the Offer: 2022
Company: Google
Title/Level : L3
Location: Bangalore
Salary: ₹28,50,000
Bonus: ₹3, 00,000
Stock: $50k stock grant vested over 4 years (33%, 33%, 22%, 12%)
Signing Bonus: ₹2,00,000
Total comp (Salary + Bonus + Stock): ₹ 41,50,000
Benefits: Standard Google benefits
Other details: One round went average where i would have got lean hire whereas all other was hire or strong hire.
Disappointed with numbers!!
```

Google | L3 | Bangalore

```
Education: BTech(CSE) from tier-III college
Years of Experience: 2.8
Prior Experience: Software Developer at service based MNC
Previous compensation : 10.8 L
Date of the Offer: 26th March 2022
Company: Phonepe
Title/Level: Software Engineer
Location: Bangalore
Salary: 25L(Base)
Relocation: As part of relocation policy
Signing Bonus: 3L
Stock bonus: 30K $ vested over 4 years
Bonus: NA
Total comp (Salary + Bonus + Stock): 33L for first year, 30L second year onwards
Benefits: Bunch of standard benefits
Other details: I don't have any other offer for negotiation

Can you guys suggest is there any scope for negotiation by counter offer?
```

Phonepe | Software Engineer | Bangalore

Few months back,one of the biggest tech giant **Github** faced a database outage and literally went off for like 2.5 hours which is a very long period when your system is heavily used by users.

![](https://pbs.twimg.com/profile_images/421046978999357440/UeJH8kdG_400x400.jpeg)

**What really happended?**

As we all know the id column (**PRIMARY** **KEY**) is always set to auto-increment in large tech systems for smooth transactions.

This lead to a massive outage on github as the range of id got exceeded and the table was not accepting any more records.

**LoopHole**

![](https://i.stack.imgur.com/lrXCt.png)

They were using **SIGNED INT** which ranges from:

*-231 (-2,147,483,648) to 231-1 (2,147,483,647)*

Now as negative ID's are never used,we are wasting *-2^31* part and that acts as a major blocker and shortens our range.

**FIX!**

We should always use **UNSIGNED INT** while creating out primary key as it increases our ranges and now the negative part is not there and wont go unused.

Now ID ranges from:

**0 ->>> 2,147,483,647 * 2**

That's it your DATABASE is **OUTAGE** free now.

How to avoid Database Outages in large scale systems? | Tips and Tricks

Usually, the System Design interviews are lengthy and cover a lot of complex components. This makes it very easy to get lost in small things and miss out on the big picture. Therefore, it becomes very important to structure your interview in a way such that you can easily convey the whole picture without wasting time on anything which does not add value.

Below is the structure that I follow, and you could try the same.


![](data:image/png;base64,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)

![](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSoiVKmd3Vha_uca4QTU8-xm8PT-mfWoYtsvmD6v4Wr_x0gpeSmyEhZuJIUmdQW5f2JYUo&usqp=CAU)

**Drive the interview**

Make sure you are the one driving the interview and not your interviewer. This does not mean that you do not let them speak, but rather, you should be the one doing most of the talking, proactively calling out issues in your design before the interviewer points it out, handle the edge cases that the interviewer might poke you on etc.

**FRs and NFRs**

Clearly call out the Functional and Non-Functional requirements.

The intent is that the requirements should be big enough that makes the problem challenging and also finite enough that you can build a system that fulfills those requirements within the stipulated time. From the Non Functional side, try to make a system that works at a very large scale. What's the fun in designing a system which works at a low scale?

Before finalizing the FRs and the NFRs, get them reviewed with your interviewer to make sure they do not want to add/ remove something. At times, interviewers do have some particular use cases in mind that they want to go over.

**Capacity Estimation**

Check with your interviewer if they want to get into this. A lot of people prefer to skip the calculations and focus more on the design, assuming a large enough approximate number for the number of cores required or the amount of disk required etc.

**Plan**

Based on the FRs and NFRs, come up with these things:

- User Interaction Points.
- Latency/ Availability/ Consistency requirements at each of the user interaction points.
- A quick analysis estimating if it's a read-heavy interaction or a write-heavy interaction.
- Based on the above three, come up with what all services you'll need and what kind of databases you can use to store the data that each of these services owns.


**HLD** 

Come up with a high level component diagram, that covers the following:

- What all services are present? Make sure you divide the flow into multiple functional components and see if a microservices based approach makes sense or not.
-  Usually, using a microservices based approach is a good idea in SD interviews.
- How do the services interact with each other and what kind of protocols are used for inter service communication like Async/ Sync - Rest, RPC etc?
- How would the users interact with the whole system and what all services are user facing. 
- Do you need a Cache to reduce latencies?
- Which service uses what Database and why? [You can refer to this article that can help you choose the right database based on your use case](https://www.codekarle.com/system-design/Database-system-design.html)
- See if you need caching anywhere and if you do, then what shall be the eviction policy, do you need an expiry for the keys, should it be a write through cache etc?
- Basis all this analysis, draw out a High Level Diagram of your whole system.

**Must Haves**

Some key things your high level diagram should have are:

- Load Balancers
- Services
- Databases and Caches
- User interaction points
- Any other tools like a Message Queue, CDN, etc.

**Walkthrough the design**

Once you have the whole diagram ready, go over the whole design, one use case at a time and explain your design to your interviewer at a very high level.
Talk about why you have chosen a particular database here and why you have used a particular mode of communication like Sync/ Async etc. You can also get into an RPC vs HTTP kind of a conversation if you made a particular design choice. You should go over what kind of data replication strategy is being used in your databases, for example, would you use a Master-Slave or a Multi Master setup etc.

If this sounds intimidating, you can check out how I usually do a design walkthrough in this video.



**CAUTION**: Do not go into the details like APIs, DB Schema etc right away unless the interviewer asks for it. Most people get lost in designing the APIs for just one system at this point and run out of time later on.

**Brownie Points**: Most interviews do not have FRs and NFRs around analytics, but if your design covers that or leaves good enough scope for analytics, that elevates your solution a lot. Try to add that. [For example, you can look at this](https://www.codekarle.com/system-design/Amazon-system-design.html).

This video also covers Analytics in great depth.

[Check this Video out.](https://www.youtube.com/watch?v=EpASu_1dUdE)

**Implementation**

Once you explain the whole flow to your interviewer, ask them which component they want to discuss in detail. Usually, people do not want to go over the entire system in detail. Let them decide which is that one component that they want to dig into and then you can go over the implementation details of that particular system.
Things you should cover here are:

1. APIs- Call out the APIs that this system exposes. Make sure you are using the best practices here. For example instead of a GET API with URL like GET /user/getUserbyUserId, it’s better to use: GET /user/{id}
2. API Protocols - You can cover what protocols are you exposing the APIs on. Most people choose REST APIs, but you can decide to use something more efficient like Thrift, Protobuf etc based on your use cases.
3. Events - You can call out which events this particular service listens to, who produces that event, what payload comes in, what processing happens on that event etc.
4. DB Schema - Go over the DB Schema here. You can also get into SQL vs NoSQL debate or why have you chosen a particular database, if you did not go over the same earlier while talking about the high level design.
5. If it's a SQL, do talk about what indices you'll have and how are you optimising your queries. In case of NoSQL, make sure you go over the consistency guarantees that the DB provides, can it cause any issues and the kind of queries you'll run on that DB. Clearly call out the keys for key-value stores or the partition keys for a columnar store etc.

**Handle Murphy's law**

This is something that most people skip but this is one of the most important things that you must cover which talks about how resilient your system is. In the real world, things break, and when they do, you need to make sure you are in full control of your system.

Talk about how you monitor the system. What kind of alerting mechanism do you have in place? What are your KPIs (Key Performance Indicators) and how do you track them? What happens when things break, when your service crashes, your DB's master node goes down or even when one of your datacentres goes down?

Again, if you haven't done this before, [see how I have been doing it, towards the later half of this video.](https://www.youtube.com/watch?v=YyOXt2MEkv4)



This is my checklist, that I usually follow when I try to design any system, be it in an interview or in the real world.

Thoughts/Suggestions?

Crack System Design Interviews Roadmap | The Ulimate Guide.

This is a post about how I lost way, found it back, and then went from 6 to 45+ LPA in two years, and from being called "just a QA" to a Senior Software Engineer and it is going to be a long one :D

![](data:image/png;base64,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)

**THE BEGINNINGS:-**

In 2016, I graduated from a "Tier - 3 university" in B. Tech(CS). Upon graduation, I joined a service-based IT company in Gurgaon, India.

The company had visited our campus for the first time and offered the highest comp among all on-campus companies, 5.25 LPA. Parents wanted me to join as the offer was good and there was a financial situation at home. I was also preparing for GATE(Exam for admission into M. Tech at Indian universities) which I needed to give up if joining.

Initially our college didn't inform us about the role being offered. Just one week before joining, I found out from one of the selected students having connections in the placement department that this was a testing role. With no other option and only a week to go, I had to join.

**THE HOPELESSNESS**:-

Within a month I realized this wasn't for me. I always liked programming, but couldn't do it here. The job was manual testing. All efforts put in college, subjects studied, projects made, and the preparation for GATE seemed to be of no use. After six months, I wanted to quit, drop a year and restart my preparation for GATE but I just didn't have the option to stop working.

Also, in the industry non-technical manual QA isn't taken seriously. This is especially true in service-based companies, even though they are a part of every project! One time, I was returning from the cafeteria with my PM, Dev Manager, and two friends from the QA team. Both managers started talking about how there is no need for QA and they don't do anything significant, right infornt of us! Even some of my developer friends used to joke about it by saying things like "you're just a QA" or "this guy wants to do full-stack(sarcastically)" when I would ask them about development. Such experiences can be highly demotivating, especially for people in the initial stages of their careers but these experiences and phrases would eventually become my driving force.

After around 1.5 years, working as a manual QA, things had come to a point where I wanted to quit the tech industry entirely. I felt like I could never code again. The stigma associated with the role, non-technical, non-challenging work, and the stagnant pay were killing me.

I started exploring all kinds of options, like preparing for public sector/govt. jobs(SSC, PSUs), starting a business, and even preparing for civil services. Time passed and everything piled up. Eventually I was left with no motivation and hope about the future.

**THE STRUGGLE**:-

After a year of all this, I decided that the next best thing would be to learn automation testing. Being out of touch with coding for almost 2.5 years, it took me ten months to just learn the basics of Java and basic problem-solving. Just around then, a few of my colleagues got offers of 10-15 LPA from mid-size product-based companies, most of them as SDEs but some also as SDETs. Seeing people from my team getting offers from product-based companies also motivated me. I learned about their interview experiences and how they had prepared. I picked up the speed on my preparation. In the next two months, I finished the remaining topics. I started applying to companies for SDET and got my first interview scheduled with Nagarro. I reached the third and last round, which didn't go well, and they put me on hold. A month later, I got my first offer of 10 LPA from TestVagrant in Bangalore for an SDET role. My comp was 6 LPA at that time, so 10 LPA was a hike of around 65%. I finally resigned from my job!
I also got offers from Deloitte, Sprinklr, with Naggaro again, and the company I eventually joined for 12.5 LPA for as an SDET.

After 3.5 years of struggle and hopelessness, I had five offers with decent compensation, better than a lot of people who doubted me, and a much more technical role than manual testing.

**THE GROWTH**:-

After joining my second company, the initial 3-4 months were extraordinarily difficult for me. I struggled in understanding the architecture, the databases, the mappings of different tables, debugging the application logs, doing environment setups, and doing prod releases. I would get lost in the automation codebase as it was so huge.
Almost all the tech was new to me. Only thing I knew was programming and basic automation.

But I coped up, mainly because I was getting the these three things which I didn't get in my previous organization:-

Opportunity. Opportunity to code and do technical work.
Freedom. Freedom to go deep into the technologies getting used, having access to all codebases.
Support. A lot of support from some great mentors - mainly my lead, all the developer friends, and the dev manager of my team.
As I got more comfortable, I learned the basics of Spring and microservice architecture. I got access to different codebases and understood them. I went through the code of APIs and understood them in and out. Whatever feature I would test, I would first look at the code changes. I understood the databases, learned how to debug different kinds of issues, and documented everything!
I contributed a lot to the automation suite and infrastructure. Even used to fix some product bugs that I would report, implemented some small features when devs were tight on bandwidth.

After about a year, I grew a lot technically with a good understanding of all technologies we used in the architecture. I became one of the most recognized SDETs in the company. In two years, my compensation also went from 12.5 LPA to 18 LPA + ESOPs.

**THE FINAL STEP**:-

Last year in March-April, a friend in my team introduced me to Leetcode. The monthly challenges had just started, and I also started with those. I wasn't very consistent and was only solving to get comfortable with DSA, having been out of touch for a year. I had solved around 250 problems repeatedly by September, learned about design, especially in test automation, and started interviewing for SDET - II roles just to test my preparation levels. I got offers from Paytm(18 LPA), WhatFix(23 LPA), Nykaa(16 LPA), MindTickle(25 LPA) in Oct-Nov 2020. I interviewed at GoJek and reached the last VP round.

While I was applying to these companies initially, I had also applied to Facebook from their careers portal, and got an unexpected callback! I interviewed at FB but got rejected in the first on-site round.
However, getting a call back from FB had installed a faith in me that getting into bigger and higher-paying tech companies was also possible. My background would not matter as much as I thought if I put in more effort in preparation.

So I rejected all the offers and started preparing more seriously. I solved a total of 330 questions repeatedly by March of this year. I interviewed at Meesho for SDET-III and Cred for SDET(flat hierarchy) to check my preparation and got rejected. I also appeared for PhonePe for a SET role, cleared the first round in problem-solving but couldn't clear the next round on Automation and Design. I needed to work more on technical skills, designing and scaling the framework, and library related interview questions, but I was doing well in problem-solving.

One of my friends had joined InMobi at that time, got a referral for SDET-III in Inmobi Glance, interviews were scheduled. All rounds had questions on problem-solving. The HM round had detailed project-related, technical, and automation design, for which I had prepared a lot by then. I cleared all the rounds, especially the HM round went great, and I was offered 35 L + 1000 RSUs (32 Base + 3 L PF, Gratuity and Benefits + 1000 RSUs)!

I accepted the offer and resigned from my second company. I was also interviewing with Zeta, Games 24x7, Hotstar, and a good product-based company, that I eventually joined as a SSE. I got selected in Games 24x7 and offered a 38 L (36.25 Base + 0.25 PF + 1.5 Joining Bonus) for SDET-II. I also got selected in Zeta for Sr. SDET but asked them to not prepare the offer as I had decided to join the company I am currently at. I was at the last round with Hotstar and canceled the interview process for the same reason. Upon declining InMobi Glance's offer, they bumped it to around 45.5 L + 1000 RSUs (38 Base + 2.5 Benefits + 5 Joining Bonus + 1000 RSUs). I chose to reject it and go with the other offer I mentioned before as the work was much more technical and comp for later years was higher.

In all this I went from 6 to 45+ LPA in two years starting as a manual tester. I wanted to contribute to the LC community and help people having the same struggles as I have had from the experiences I have gained. Hopefully, it motivates a few people here.

Journey from 6LPA to 45LPA in 2 years | Programming Motivation

Programming Languages are one of the most effective and dangerous tools one can have when they are building their careers.

In the Present world,around 60% of day to day works rely on huge systems made out of programming languages and today we are going to discuss 5 programming languages you should focus on in 2022.

- JAVA

![](https://image.chitra.live/api/v1/wps/cfbae39/c170971a-89d8-4075-9007-72c0bb5f5013/4/java-580x358.png)

Java is one of the most used and reliable programming language when it comes to building distributed backend systems or be it making fast day to day computations.

Java is one of the oldest players in this community and yet their demands keeps on increasing day by day and it aint stopping soon.One of the strong reasons it is still used this heavely in Tech industry is because of its considered to be the pillar of programming and it teaches us how to design system the **OBJECT ORIENTED WAY**.

- Python

![](https://www.seekpng.com/png/small/333-3336903_python-language-icon-python-programming-language-icon.png)

If Python doesnt makes it to this list I dont know who will,Python is one of the best scripting language out there,Want to automate something? Go Python , Want easy to use scripts? Go python and thats why Python finds its place in every backend systems ever built and will be build.

Python also makes it to the list due to its easy to use and understandable syntax which makes it pretty easy to learn.

- Javascript

![](https://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/JavaScript-logo.png/480px-JavaScript-logo.png). 

Now its time to introduce the well known and the most used programming language in the world i.e **JAVASCRIPT**.
Everything we see on web is Javascript.you open Google,its javascript.you make the next google,well its also javascript.

The Versatility Javascript shows is how it made it to this list.

1. Android Apps - React Native(Javascript)
2. IOS Apps - React Native(Javascript)
3. Web apps - React JS(Javascript)
4. Web Servers - NodeJS(Javascript)

And thats why its the king of all the languages.

- GoLang

![](https://styles.redditmedia.com/t5_2rc7j/styles/communityIcon_wy4riduoe9k11.png)

If you're coming from Java, learning Go will help you learn a different way of decomposing the program structure (Interfaces and Composition instead of Classes and Inheritance) and also help you get similar amount of work done with less code while giving comparable performance with multi-threaded server code.

If you're coming from Python/Ruby, learning Go will help you write programs with almost similar level of productivity while boosting the runtime performance and multi-core exploitability of most of your server-side code

If you're coming from PHP, learning Go will help you write much more robust code with strong, static type checking, it'll improve your productivity with a strong debugging and profiling toolchain, it'll help you write concurrent programs easily and it'll speed up your average server-side application quite a bit.

If you want to learn a new language to be able to set yourself apart from peers, Go might be your biggest competitive advantage from a languages point-of-view. It's easy to learn and it provides tangible benefits when deployed in production.

- C++

![](https://upload.wikimedia.org/wikipedia/commons/1/18/ISO_C%2B%2B_Logo.svg)

We use C++ because we have real-time critical safety performance requirements, and for that, there are no other things, besides C. Furthermore, today's AI industry is basically built upon c++. AI scientist, data analyst may prefer simple language bindings like python, but any serious project has to use c++ in its very core. C++ will continue to be used by many companies in the autonomous driving space for the foreseeable future.

C++ is also commonly used in embedded devices and in firmware for all kinds of stuff. C++ also has the advantage that it is an open ISO standard not owned or controlled by any one corporation in the way that e.g. Java, Swift, C# are. This might matter less to you than it does to me.

1. High Performance Computing - C++ is one of the few high level languages with high performance and and direct access to the operating system system calls that are exposed in C. Examples of HPC are programming related to physics, finance, fluid mechanics, finite element methods, games engines and so on.
2.  Develop firmware for embedded systems such as microntrollers and embedded processors for controlling home appliances, car's fuel injection, motors, robots and so on. Those systems have memory constraints and many of them doesn't even have operating system.
3.  High performance software components or libraries - It is possible to write libraries of higher level programming languages in C++ and getting the best of both worlds, for instance, one could write high performance python, java, R or C# libraries in C++. And also Excel addins in C++.
4.  Take full advantage of the operating system - It means developing any program that requires access to all OS features and, graphical stack and system calls.

5. Low level stuffs - Device driver, interface hardware ..

Top Programming Languages to learn in 2022!

The database index is a data structure that improves the speed of data retrieval operations on a table at the cost of additional writes and storage space. Mostly, it's a copy of selected columns of data from a single table. We should create indexes to increase performance of our Database.

To add indexing in your database, @Index annoation is used which is basically a java interface that helps our entity tables get indexed with the columns you like.

```
@Target({}) 

@Retention(RUNTIME) 

public @interface Index 

{ 

String name() default ""; 

String columnList(); 

boolean unique() default false; 

}

```

Index just creates a extra storage layer above our original table only with the columns that we specify in our index and thats how its highly efficient and fast.

As you can see in the predefined Index Interface that it has 4 fields that helps us to configure our indexing to any table.

- name - the name you want to give your index. (not mandatory as if not provided JPA will use a random name)
- columnList - the columns that will the present in your index and its a mandatory field.
- unique - this field can be set to true or false based on whether the columns your are indexing contains duplicate records or not. If they contains duplicate records set this to false  and if it has unique records set it as true which is also its default behaviour.
Lets apply indexing to our database now:

**Our Entity**

```
@Entity 

@Table 

public class Student 

{ 

@Id 

@GeneratedValue 

private Long id; 

private String firstName; 

private String lastName; 

// getters, setters 

}
```

Now this is how our table looks like and now we have to index it.

- Just adding columns

```
@Table(indexes = @Index(columnList = "firstName"))
 

```

As the columnList is a mandatory field and must be provided along with index annotation,in the above example we have just provided that.

- Adding index name to our index

`@Index(name = "fn_index", columnList = "firstName")`

- Adding multiple columns to our index

```
@Index(name = "mulitIndex1", columnList = "firstName, lastName") 

@Index(name = "mulitIndex2", columnList = "lastName, firstName")

```

- Adding order to index (default ASC)

`@Index(name = "mulitSortIndex", columnList = "firstName, lastName DESC")`

order is used  to set the sort order of the values in the indexed column.

- Adding uniqueness to our index

`@Index(name = "uniqueIndex", columnList = "firstName", unique = true)`

A unique index ensures that the indexed fields don't store duplicate values. By default, it's false. If we want to change it, we can declare it as above.

**Lets aggregate what we have learned till now and apply it on a table to get the final understanding:**

```
@Entity 

@Table(indexes = { 

@Index(columnList = "firstName"), 

@Index(name = "fn_index", columnList = "firstName"), 

@Index(name = "mulitIndex1", columnList = "firstName, lastName"), 

@Index(name = "mulitIndex2", columnList = "lastName, firstName"), 

@Index(name = "mulitSortIndex", columnList = "firstName, lastName DESC"), 

@Index(name = "uniqueIndex", columnList = "firstName", unique = true), 

@Index(name = "uniqueMulitIndex", columnList = "firstName, lastName", unique = true) }) 

public class Student implements {

@Id 

@GeneratedValue 

private Long id; 

private String firstName; 

private String lastName; 

// getters, setters 

}
```

That's it for Indexing for now,Hope you liked it.

Do comment and tell me what topics do you want next

Latest Posts.

initState and didChangeDependencies methods in Flutter Explained | Flutter Tips and Tricks

devdad

initState()

Sorting Algorithms Analyzer/Visualizer using Flutter | Best Flutter Project for Students | Flutter Developers

devdad

So,Let’s get started.

Realtime Dog Breed Detection using Flutter | Machine Learning With Flutter | TensorFlow and Flutter

devdad

Dog Breed Identification App with Flutter and tflite in 10 mins.

Make a Phone Call using Flutter App | Easy Flutter Tutorials

devdad

Today we are going to talk about how easy it is to call someone directly from your flutter app so that it can be implemented in a real-time working application.

Using Image Picker with Flutter and storing images in Local Storage | Quick Flutter Guide | Mobile App Development

devdad

So, Today we are gonna talk about and understand how we can import images from ‘ON-DEVICE STORAGE’ or ‘CAMERA’ to our flutter apps and store it in device storage too.

There are 3 Dart packages you’ll need to implement this: