DENDQ

#include<stdio.h>
#include<stdlib.h>
#define SIZE 3
void insert(int a[]);
void Delete(int a[]);
void display(int a[]);
int rear=-1,front=-1;
int main()
{
	int a[SIZE],choice;
	while(1)
	{
		printf("1.insert\n2.delete\n3.display\n4.exit\nenter choice:");
		scanf("%d",&choice);
		switch(choice)
		{
			case 1:insert(a); break;
			case 2:Delete(a); break;
			case 3:display(a); break;
			case 4: exit(0); 
			default : printf("invalid choice\n");
		
		
		}
	
	}

}

void insert(int a[])
{
	int opt;
	if ((rear+1)%SIZE==front && rear!=-1)
		printf("overflow\n");
	else
	{
		printf("1.insert_front\n2.insert_rear\nenter choice");
		scanf("%d",&opt);
		switch (opt)
		{
			case 1: if (front==-1)
					{	front=0;
						rear=0;
					}
					else if(front==0)
						front=SIZE-1;
					else
						front--;
					printf("enter data:");
					scanf("%d",&a[front]);
					break;
			case 2: if (rear==-1)
					{	front=rear=0;
					
					}
					else
						rear=(rear+1)%SIZE;
						
					printf("enter data:");
					scanf("%d",&a[rear]);
					break;
			default:
				printf("invalid\n");
		}
	
	
	
	}
		

}

void Delete(int a[])
{
	int opt;
	if (front==-1)
		printf("underflow\n");
	else
	{
		printf("1.delete_front\n2.delete_rear\nenter choice");
		scanf("%d",&opt);
		switch (opt)
		{
			case 1: printf("dequed element:%d\n",a[front]);
					if(front==rear)
						{	front=-1;
							rear=-1;
						
						}
					else 
					{front=(front+1)%SIZE;}
					break;
			case 2: printf("dequed element:%d\n",a[rear]);
					if(rear==front)
					{
						front=rear=-1;
					
					}
					else if(rear==0)
						rear=SIZE-1;
					else
						rear--;
					break;
			default:
				printf("invalid\n");
		}
	
	
	
	}
	
	

}

void display(int a[])
{	int i;
	if (front==-1)
		printf("queue emplty\n");
	else
	{	printf("queue is:\n");
		if (front<=rear)
		{
			for(i=front;i<=rear;i++)
			{
				printf("%d\n",a[i]);
			}
		}
		else
		{
			for(i=front;i<SIZE;i++)
			{
				printf("%d\n",a[i]);
			}
			for(i=0;i<=rear;i++)
			{
				printf("%d\n",a[i]);
			}
		
		}
	}
	
	


}