/* Program of queue using circular linked list*/
# include <stdio.h>
# include <stdlib.h>
struct node
{
int info;
struct node *link;
}*rear=NULL;
main()
{
int choice;
while(1)
{
printf("1.Insert \n");
printf("2.Delete \n");
printf("3.Display\n");
printf("4.Quit\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
insert();
break;
case 2:
del();
break;
case 3:
display();
break;
case 4:
exit();
default:
printf("Wrong choice\n");
}/*End of switch*/
}/*End of while*/
}/*End of main()*/
insert()
{
int num;
struct node *q,*tmp;
printf("Enter the element for insertion : ");
scanf("%d",&num);
tmp= malloc(sizeof(struct node));
tmp->info = num;
if(rear == NULL) /*If queue is empty */
{
rear = tmp;
tmp->link = rear;
}
else
{
tmp->link = rear->link;
rear->link = tmp;
rear = tmp;
}
}/*End of insert()*/
del()
{
struct node *tmp,*q;
if(rear==NULL)
{
printf("Queue underflow\n");
return;
}
if( rear->link == rear ) /*If only one element*/
{
tmp = rear;
rear = NULL;
free(tmp);
return;
}
q=rear->link;
tmp=q;
rear->link = q->link;
printf("Deleted element is %d\n",tmp->info);
free(tmp);
}/*End of del()*/
display()
{
struct node *q;
if(rear == NULL)
{
printf("Queue is empty\n");
return;
}
q = rear->link;
printf("Queue is :\n");
while(q != rear)
{
printf("%d ", q->info);
q = q->link;
}
printf("%d\n",rear->info);
}/*End of display()*/
