/*
Write a program of circular queue
*/
#include<stdio.h>
#include<stdlib.h>
#define MAX 10
int cqueue_arr[MAX];
int front=-1;
int rear=-1;
void display( );
void insert(item);
int del();
int peek();
int isEmpty();
int isFull();
main()
{
int choice,item;
while(1)
{
printf("1.Insert\n");
printf("2.Delete\n");
printf("3.Peek\n");
printf("4.Display\n");
printf("5.Quit\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1 :
printf("Input the element for insertion : ");
scanf("%d",&item);
insert(item);
break;
case 2 :
printf("Element deleted is : %d\n",del());
break;
case 3:
printf("Element at the front is : %d\n",peek());
break;
case 4:
display();
break;
case 5:
exit(1);
default:
printf("Wrong choice\n");
}
}
}
void insert(int item)
{
if( isFull() )
{
printf("Queue 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 ;
}
int del()
{
int item;
if( isEmpty() )
{
printf("Queue 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;
}
int isEmpty()
{
if(front==-1)
return 1;
else
return 0;
}
int isFull()
{
if((front==0 && rear==MAX-1) || (front==rear+1))
return 1;
else
return 0;
}
int peek()
{
if( isEmpty() )
{
printf("Queue Underflow\n");
exit(1);
}
return cqueue_arr[front];
}
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 ",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");
}
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