Question

in java, starting with an empty list, show conents of an array (including their index), size 4, implimenting a circular queue after the following operations are performed:

insert(2)

insert(7)

insert(9)

delete()

delete()

insert(5)

detete()

delete()

insert(15)

Answer 1

Java Code:

import java.util.*;

class queue

{

    int rear,front;

    int size;

    int arr[];

    queue(int n)

    {

        this.front=this.rear=-1;

        this.size=n;

        arr = new int[n];

    }

    void insert(int value)

    {

        //Queue is full

        if((front == 0 && rear == -1) || (rear==(front-1)%(size-1)))

        {

            System.out.println("Queue is full\n");

            return;

        }

        //Queue is empty inserting first element

        else if(front == -1)

        {

            front = rear = 0;

            arr[rear]=value;

        }

        //inserting after deletion

        else if (rear == size-1 && front != 0)

        {

            rear = 0;

            arr[rear] = value;

        }

        //normal insertion

        else

        {    

            rear++;

            arr[rear] = value;

        }

    }

    int delete()

    {

        //Queue is empty if front=-1

        if(front == -1)

        {

            System.out.println("Queue is empty");    

            return -1;

        }

        //storing the deleting element in del

        int del = arr[front];

        //setting the index of deleted item to -1

        arr[front]= -1;

        if (front == rear)

        {

            front=rear=-1;

            //after this Queue is empty

        }

        else if(front == size-1)

            front=0;

        else

            front++;

        return del;

    }

    void display()

    {

        int i;

        if(front == -1)

        //Queue is empty if front=-1

        {

            System.out.println("Queue is empty\n");

            return;

        }

        System.out.println("Elements in circular Queue are:");

        System.out.println("Element  Index");

        if(rear >= front)

        //normally with doing circulation

        {

            for(i=front;i<=rear;i++)

            {

                System.out.println(arr[i]+"        "+i);

            }

        }

        else

        {

            for(i=front;i<size;i++)

                System.out.println(arr[i]+"        "+i);

            for(i=0;i<=rear;i++)

                System.out.println(arr[i]+"        "+i);

        }

    }

}

public class Main

{

    public static void main(String[] args) {

        queue obj = new queue(4);

        //inserting into Queue

        obj.insert(2);

        obj.insert(7);

        obj.insert(9);

        obj.display();

        //Deleting from Queue

        obj.delete();

        obj.delete();

        obj.display();

        //Insertion after deletion

        obj.insert(5);

        obj.display();

        //deleting all the Elements from queue

        obj.delete();

        obj.delete();

        obj.display();

        //insering 15 into empty queue

        obj.insert(15);

        obj.display();

    }

}

Output:

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