C Program of dequeue using a circular array

Data Structure / Queue Data Structure

760

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Program:

/* C Program of dequeue using a circular array*/
#include<stdio.h>
#include<stdlib.h>
#define MAX 7

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

void insert_frontEnd(int item);
void insert_rearEnd(int item);
int delete_frontEnd();
int delete_rearEnd();
void display();
int isEmpty();
int isFull();

main()
{
	int choice,item;
	while(1)
	{
		printf("1.Insert at the front end\n");
		printf("2.Insert at the rear end\n");
		printf("3.Delete from front end\n");
		printf("4.Delete from rear end\n");
		printf("5.Display\n");
		printf("6.Quit\n");
		printf("Enter your choice : ");
		scanf("%d",&choice);

		switch(choice)
		{
		case 1:
			printf("Input the element for adding in queue : ");
			scanf("%d",&item);
			insert_frontEnd(item);
			break;
		case 2:
			printf("Input the element for adding in queue : ");
			scanf("%d",&item);
			insert_rearEnd(item);
			break;
		 case 3:
			printf("Element deleted from front end is : %d\n",delete_frontEnd());
			break;
		 case 4:
			printf("Element deleted from rear end is : %d\n",delete_rearEnd());
			break;
		 case 5:
			display();
			break;
		 case 6:
			exit(1);
		 default:
			printf("Wrong choice\n");
		}/*End of switch*/
		printf("front = %d, rear =%d\n", front , rear);
		display();
	}/*End of while*/
}/*End of main()*/

void insert_frontEnd(int item)
{
	if( isFull() )
	{
		printf("Queue Overflow\n");
		return;
	}
	if( front==-1 )/*If queue is initially empty*/
	{
		front=0;
		rear=0;
	}
	else if(front==0)
		front=MAX-1;
	else
		front=front-1;
	deque_arr[front]=item ;
}/*End of insert_frontEnd()*/

void insert_rearEnd(int item)
{
	if( isFull() )
	{
		printf("Queue Overflow\n");
		return;
	}
	if(front==-1)  /*if queue is initially empty*/
	{
		front=0;
		rear=0;
	}
	else if(rear==MAX-1)  /*rear is at last position of queue */
		rear=0;
	else
		rear=rear+1;
	deque_arr[rear]=item ;
}/*End of insert_rearEnd()*/

int delete_frontEnd()
{
	int item;
	if( isEmpty() )
	{
		printf("Queue Underflow\n");
		exit(1);
	}
	item=deque_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 delete_frontEnd()*/

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

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

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

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

Output:

1.Insert at the front end
2.Insert at the rear end
3.Delete from front end
4.Delete from rear end
5.Display
6.Quit
Enter your choice : 1
Input the element for adding in queue : 12
front = 0, rear =0
Queue elements :
12
1.Insert at the front end
2.Insert at the rear end
3.Delete from front end
4.Delete from rear end
5.Display
6.Quit
Enter your choice : 2
Input the element for adding in queue : 14
front = 0, rear =1
Queue elements :
12 14
1.Insert at the front end
2.Insert at the rear end
3.Delete from front end
4.Delete from rear end
5.Display
6.Quit
Enter your choice : 3
Element deleted from front end is : 12
front = 1, rear =1
Queue elements :
14
1.Insert at the front end
2.Insert at the rear end
3.Delete from front end
4.Delete from rear end
5.Display
6.Quit
Enter your choice : 45
Wrong choice
front = 1, rear =1
Queue elements :
14
1.Insert at the front end
2.Insert at the rear end
3.Delete from front end
4.Delete from rear end
5.Displa

Explanation:

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