C Program to implement circular queue using arrays

By | 10.04.2017

Circular queue using arrays


Write a C Program to implement circular queue using arrays. Here’s simple Program to implement circular queue using arrays in C Programming Language.


What is Queue ?


Queue is also an abstract data type or a linear data structure, in which the first element is inserted from one end called REAR, and the deletion of existing element takes place from the other end called as FRONT.

This makes queue as FIFO data structure, which means that element inserted first will also be removed first.


Basic Operations : :


  • enqueue() − add (store) an item to the queue.
  • dequeue() − remove (access) an item from the queue.
  • peek() − Gets the element at the front of the queue without removing it.
  • isfull() − Checks if the queue is full.
  • isempty() − Checks if the queue is empty.

Below is the source code for C Program to implement circular queue using arrays which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/* C Program to implement circular queue using arrays  */

#include<stdio.h>
#include<stdlib.h>
#define MAX 10

int cqueue_arr[MAX];
int front=-1;
int rear=-1;

void display( );
void insert(int item);
int del();
int peek();
int isEmpty();
int isFull();

int main()
{
        int choice,item;
        while(1)
        {
                printf("\n1.Insert\n");
                printf("2.Delete\n");
                printf("3.Peek\n");
                printf("4.Display\n");
                printf("5.Quit\n");
                printf("\nEnter your choice : ");
                scanf("%d",&choice);

                switch(choice)
                {
                case 1 :
                        printf("\nInput the element for insertion : ");
                        scanf("%d",&item);
                        insert(item);
                        break;
                case 2 :
                        printf("\nElement deleted is : %d\n",del());
                        break;
                case 3:
                        printf("\nElement at the front is  : %d\n",peek());
                        break;
                case 4:
                        display();
                        break;
                case 5:
                        exit(1);
                default:
                        printf("\nWrong choice\n");
                }/*End of switch*/
        }/*End of while */

        return 0;

}/*End of main()*/

void insert(int item)
{
        if( isFull() )
        {
                printf("\nQueue Overflow\n");
                return;
        }
        if(front == -1 )
                front=0;

        if(rear==MAX-1)/*rear is at last position of queue*/
                rear=0;
        else
                rear=rear+1;
        cqueue_arr[rear]=item ;
}/*End of insert()*/

int del()
{
        int item;
        if( isEmpty() )
        {
                printf("\nQueue Underflow\n");
                exit(1);
        }
        item=cqueue_arr[front];
        if(front==rear) /* queue has only one element */
        {
                front=-1;
                rear=-1;
        }
        else if(front==MAX-1)
                front=0;
        else
                front=front+1;
        return item;
}/*End of del() */

int isEmpty()
{
        if(front==-1)
                return 1;
        else
                return 0;
}/*End of isEmpty()*/

int isFull()
{
        if((front==0 && rear==MAX-1) || (front==rear+1))
                return 1;
        else
                return 0;
}/*End of isFull()*/

int peek()
{
        if( isEmpty() )
        {
                printf("\nQueue Underflow\n");
                exit(1);
        }
        return cqueue_arr[front];
}/*End of peek()*/

void display()
{
        int i;
        if(isEmpty())
        {
                printf("\nQueue is empty\n");
                return;
        }
        printf("\nQueue elements :\n");
        i=front;
        if( front<=rear )
        {
                while(i<=rear)
                        printf("%d ",cqueue_arr[i++]);
        }
        else
        {
                while(i<=MAX-1)
                        printf("%d ",cqueue_arr[i++]);
                i=0;
                while(i<=rear)
                        printf("%d ",cqueue_arr[i++]);
        }
        printf("\n");
}/*End of display() */

OUTPUT : :


/* C Program to implement circular queue using arrays  */

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 1

Input the element for insertion : 1

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 1

Input the element for insertion : 2

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 1

Input the element for insertion : 3

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 1

Input the element for insertion : 4

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 4

Queue elements :
1 2 3 4

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 2

Element deleted is : 1

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 2

Element deleted is : 2

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 2

Element deleted is : 3

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 3

Element at the front is  : 4

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 4

Queue elements :
4

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 2

Element deleted is : 4

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 4

Queue is empty

1.Insert
2.Delete
3.Peek
4.Display
5.Quit

Enter your choice : 5

Process returned 1

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