dequeue.c

#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();
int main()
{
 int choice,item;
 while(1)

 {
 printf("\n\n1.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("\nEnter your choice : ");
 scanf("%d",&choice);
 switch(choice)
 {
 case 1:
 printf("\nInput the element for adding in queue : ");
 scanf("%d",&item);
 insert_frontEnd(item);
 break;
 case 2:
 printf("\nInput the element for adding in queue : ");
 scanf("%d",&item);
 insert_rearEnd(item);
 break;
 case 3:
 printf("\nElement deleted from front end is : %d\n",delete_frontEnd());
 break;
 case 4:
 printf("\nElement deleted from rear end is : %d\n",delete_rearEnd());
 break;
 case 5:
 display();

 break;
 case 6:
 exit(1);
 default:
 printf("\nWrong choice\n");
 }
 printf("\nfront = %d, rear =%d\n", front , rear);
 display();
 }
}
void insert_frontEnd(int item)
{
 if( isFull() )
 {
 printf("\nQueue Overflow\n");
 return;
 }
 if( front==-1 )
 {
 front=0;
 rear=0;
 }
 else if(front==0)
 front=MAX-1;
 else
 front=front-1;
 deque_arr[front]=item ;
}
void insert_rearEnd(int item)
{
 if( isFull() )
 {
 printf("\nQueue Overflow\n");
 return;
 }
 if(front==-1)
 {
 front=0;
 rear=0;
 }
 else if(rear==MAX-1)
 rear=0;
 else
 rear=rear+1;
 deque_arr[rear]=item ;
}
int delete_frontEnd()
{
 int item;
 if( isEmpty() )
 {
 printf("\nQueue Underflow\n");
 exit(1);
 }
 item=deque_arr[front];
21
 if(front==rear) 
 front=-1;
 rear=-1;
 }
 else
 if(front==MAX-1)
 front=0;
 else
 front=front+1;
 return item;
}
int delete_rearEnd()
{
 int item;
 if( isEmpty() )
 {
 printf("\nQueue Underflow\n");
 exit(1);
 }
 item=deque_arr[rear];
 if(front==rear) 
 {
 front=-1;
 rear=-1;
 }
 else if(rear==0)
22
 rear=MAX-1;
 else
 rear=rear-1;
 return item;
}
int isFull()
{
 if ( (front==0 && rear==MAX-1) || (front==rear+1) )
 return 1;
 else
 return 0;
}
int isEmpty()
{
 if( front == -1)
 return 1;
 else
 return 0;
}
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 ",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");
}