Queue Using Singly Linked List
#include<stdio.h>
#include<stdlib.h>
struct queue
{
int data;
struct queue *link;
};
typedef
struct queue * NODE;
NODE front = NULL;
NODE rear = NULL;
NODE
getnode()
{
NODE
x;
x
= (NODE)malloc(sizeof(struct queue));
x->link
= NULL;
}
void
insert_rear(int item)
{
int
val;
NODE
temp, cur;
temp
= getnode();
temp->data
= item;
/*Case
1: List is empty*/
if(front
== NULL)
{
front
= rear =temp;
}
else
{
rear->link
= temp;
rear
= rear->link;
}
}
NODE
delete_front()
{
NODE
temp;
if(front
== NULL)
{
printf("\nQueue
underflow");
return
NULL;
}
else
{
temp
= front;
front = front->link;
temp->link
= NULL;
printf("\nItem
got deleted is: %d", temp->data);
free(temp);
return
front;
}
}
void
display()
{
NODE
cur;
if(front
== NULL)
{
printf("\nQueue
is empty");
}
else
{
printf("\nQueue contents
are:\n");
for(cur
= front; cur != rear->link ; cur =
cur->link)
printf("%d ", cur->data);
}
}
void
main()
{
int
ch, item;
while(1)
{
printf("\n~~MENU~~");
printf("\n1.Insert
operation");
printf("\n2.Delete
operation");
printf("\n3.Display");
printf("\nEnter
your choice: ");
scanf("%d",&ch);
switch(ch)
{
case
1: printf("\nEnter the item to be inserted: ");
scanf("%d", &item);
insert_rear(item);
display();
break;
case
2: front = delete_front();
display();
break;
case
3: display();
break;
case
4: exit(0);
}
}
}
Output
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 1
Enter the item to be inserted: 11
Queue contents are:
11
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 1
Enter the item to be inserted: 12
Queue contents are:
11 12
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 1
Enter the item to be inserted: 13
Queue contents are:
11 12
13
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 1
Enter the item to be inserted: 14
Queue contents are:
11
12 13 14
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 2
Item got deleted is: 11
Queue contents are:
12
13 14
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 2
Item got deleted is: 12
Queue contents are:
13
14
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 2
Item got deleted is: 13
Queue contents are:
14
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 2
Item got deleted is: 14
Queue is empty
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 2
Queue underflow
Queue is empty
~~MENU~~
1.Insert
operation
2.Delete
operation
3.Display
Enter
your choice: 4
