/* Program to implement circular queue using linked list */
#include
#include
#define new1 (nd *)malloc(sizeof(nd))
typedef struct queue
{
int info;
struct queue *next;
}nd;
void display(nd **ptr,nd **rear)
{
nd *t=*ptr;
if(*ptr==NULL)
printf("\nQueue is empty...\n");
else
{
printf("\nQueue : ");
while(t!=*rear)
{
printf(" %d --> ",t->info);
t=t->next;
}
printf("\b\b\b\b ");
}
printf("\n");
}
void insert(nd **ptr,nd **rear)
{
nd *t=*ptr;
(*rear)->next=*ptr;
if(*ptr==NULL)
{
*ptr=new1;
printf("\nEnter 1st element : ");
scanf("%d",&(*ptr)->info);
(*ptr)->next=*rear;
}
else
{
nd *t1=new1;
printf("\nEnter element : ");
scanf("%d",&t1->info);
while(t->next!=*rear)
t=t->next;
t1->next=*rear;
t->next=t1;
}
}
void delete(nd **ptr,nd **rear)
{
nd *c=*ptr,*t=*ptr;
if(*ptr==NULL)
printf("\nQueue is empty...\n");
else if(t->next==*rear) // If head contains the address of "rear" pointer
{
*ptr=NULL;
free(t);
}
else
{
*ptr=c->next;
free(c);
}
}
main()
{
nd *h=NULL;
nd *rear=new1;
printf("\nProgram to implement circular queue using linked list : \n");
int ch;
do
{
printf("\n[1] Insert [2] Delete [3] Display [4] Exit : \n");
printf("\nEnter your choice : ");
scanf("%d",&ch);
switch(ch)
{
case 1:
insert(&h,&rear);
display(&h,&rear);
break;
case 2:
delete(&h,&rear);
display(&h,&rear);
break;
case 3:
display(&h,&rear);
break;
case 4:
break;
default : printf("\nEnter correct choice : \n");
break;
}
}while(ch!=4);
}
