Stack :
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Stack follows the principal of Last in First out

Shortened it will be called as LIFO (Last in First Out)
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Famous examples are

1. watsapp chat history
2. watsapp status history
3. In school days student note books
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In technical way recusrsion follows stack 
calling functions in a chain way follows stack principal 


Now we need to replicate stack functionality :
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using array we need to replicate stack functionalitu

8.21 to 8.30

Push
pop
peek getting peek element
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// Online Java Compiler
// Use this editor to write, compile and run your Java code online
import java.util.*;
class Main {
    static int top =-1;
    static int arr[]=new int[5];
    public static void main(String[] args) {
        System.out.println("Try programiz.pro");
        while(true){
            int opt=new Scanner(System.in).nextInt();
            switch(opt){
                case 1:
                    push(10);
                    break;
                case 2:
                    pop();
                    break;
                case 3:
                    display();
                    break;
            }
        }
        
    }
    static void push(int x){
        top++;
        arr[top]=x;
    }
    static int pop(){
        int x= arr[top];
        top--;
        return x;
    }
    
    static void display(){
        for(int i=top;i>=0;i--){
            System.out.print(arr[i]+" ");
        }
    }
    
}
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Queue:
===========

Queue follows principal first in first out

Can you give some practical examples of Queue

text messages
information will go in packets 
Booked movie tickets at cinema Hall
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Prcatical implemenation :
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1.Enque

2.Deque

3.display
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