Question

Using Java:

Provide an implementation of the LinkedQueue class by implementing it using two stacks. Submit your implementation on a java class/file called Queue2Stack.jar. You can use the implementations of stacks provided by the Java API for this exercise or you can use the LinkedStack class we implemented in class.

Answer 1

In case of any query, do comment. Please rate your answer.

Code is as below:

===================Queue2Stack.java===================

import java.util.*;

public class Queue2Stack

{

private Stack <Integer> rearStack = new Stack <Integer> ();

private Stack <Integer> frontStack = new Stack <Integer> ();

public Queue2Stack()

{

     rearStack = new Stack<>();

     frontStack = new Stack<>();

}

//add an item into the queue

public void enqueue(int x)

{

    // Enqueue will happen to rear end of the queue which is so we have to move all elements from rearStack to frontStack

    while (!rearStack.isEmpty ())

      {

                  //pop an element one by one from rear stack and push to frontStack

                  frontStack.push (rearStack.pop ());

      }

    //push it to rearstack

    rearStack.push (x);

    // then push back all items of frontStack to rearStack again

    while (!frontStack.isEmpty ())

      {

              rearStack.push (frontStack.pop ());

      }

}

// remove an item from the queue

public int dequeue()

{

    // if first stack is empty

    if (rearStack.isEmpty ())

      {

              System.out.println ("You can't remove an element from Empty Queue");

              return -1;

      }

    // Return top of rearStack

    int item = rearStack.peek ();

    rearStack.pop ();

    return item;

}

}

=================main driver program======================

public class Main

{

    public static void main(String[] args)

    {

        //create an object for Queue2Stack

        Queue2Stack queue2Stack = new Queue2Stack();

      

        //enqueue 3 items in the queue

        queue2Stack.enqueue(11);

        queue2Stack.enqueue(23);

        queue2Stack.enqueue(35);

        //dequeue the item and print it on console

        System.out.println(queue2Stack.dequeue());

        System.out.println(queue2Stack.dequeue());

        System.out.println(queue2Stack.dequeue());

        queue2Stack.dequeue(); //will show stack empty message

    }

}

===============screen shot of the code===============

Main.java Queue2Stack.java: 1 import java.util.; 3 public class Queue2Stack 4- { private Stack <Integer> rearStack = new Stack <Integer> private Stack <Integer> frontStack = new Stack <Integer> ; ; 11- 12 13 14 public Queue Stack() { rearStack = new Stack<>(); frontStack = new Stack<>(); } //add an item into the queue public void enqueue(int x) 15 16 17- // Enqueue will happen to rear end of the queue which is so we have to move all elements from rearStack to frontStack while (!rearStack.isEmpty () { //pop an element one by one from rear stack and push to frontStack frontStack.push (rearStack.pop()); //pust it to rearstack rearStack.push (x); // then push back all items of frontStack to rearStack again while (!frontStack.isEmpty () rearStack.push (frontStack.pop()); 35 // remove an item from the queue public int dequeue 36 37- // if first stack is empty if (rearStack.isEmpty ()) 40- { System.out.println("You can't remove an element from empty Queue"); return -1; // Return top of rearStack int item = rearStack.peek (); rearStack.pop(); return item;

Main.java Queue Stack.java: 1 public class Main 2 - { public static void main(String[] args), //create an object for Queue2Stack Queue2Stack queue2Stack = new Queue2Stack(); //enqueue 3 items in the queue queue2Stack.enqueue(11); queue2Stack.enqueue (23); queue2Stack.enqueue (35); //dequeue the item and print it on console System.out.println queue2Stack.dequeue System.out.println(queue2Stack.dequeue()); System.out.println queue2Stack.dequeue queue2Stack.dequeue(); //will show stack empty message } 19 20

Output:

input 23 35 You can't remove an element from Empty Queue -.. Program finished with exit code o Press ENTER to exit console.