Doubly Linked List: Delete from Front
#include<stdio.h>
#include<stdlib.h>
struct
node
{
int
data;
struct
node *llink;
struct
node *rlink;
};
typedef
struct node* NODE;
NODE getnode();
void display(NODE first);
NODE insert_at_front(NODE first, int
item);
NODE delete_at_front(NODE first);
NODE
getnode()
{
NODE
x;
x
= (NODE) malloc(sizeof(struct node));
x->llink = NULL;
x->rlink = NULL;
return
x;
}
void
display(NODE first)
{
NODE
cur;
cur
= first;
printf("\nContents
are:");
if(cur
== NULL)
printf("\nList
is empty. Nothing to display.");
else
{
while(cur!=NULL)
{
printf("%d ", cur->data);
cur = cur->rlink;
}
}
}
NODE
insert_at_front(NODE first, int item)
{
int
val;
NODE
temp;
temp
= getnode();
temp->data
= item;
if(first
== NULL)
{
return
temp;
}
temp->rlink
= first;
first->llink
= temp;
return
temp;
}
NODE
delete_at_front(NODE first)
{
NODE
temp;
if(first
== NULL) /*Case
1: List is empty*/
{
printf("\nList
is empty. Cannot delete.");
return
NULL;
}
/*Case 2: List has only one node*/
if(first->rlink == NULL)
{
printf("\nItem
that got deleted is %d", first->data);
free(first);
return NULL;
}
/*Case 3: List is not empty*/
temp
= first;
first = first->rlink;
first->llink = NULL;
printf("\nItem
that got deleted is %d", temp->data);
free(temp);
return
first;
}
void
main()
{
int
ch, item;
NODE
first = NULL;
while(1)
{
printf("\n\n~~MENU~~");
printf("\n1.Insert
at front");
printf("\n2.Delete
from front");
printf("\n3.Display");
printf("\n4.exit");
printf("\nEnter
your choice: ");
scanf("%d",
&ch);
switch(ch)
{
case
1: printf("\nEnter
the value: ");
scanf("%d",
&item);
first = insert_at_front(first, item);
break;
case
2: first = delete_at_front(first);
break;
case
3: display(first);
break;
case
4: exit(0);
}
}
}
Output:
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 1
Enter the value: 11
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 1
Enter the value: 12
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 3
Contents are:12 11
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 2
Item that got deleted is 12
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 2
Item that got deleted is 11
~~MENU~~
1.Insert
at front
2.Delete
from front
3.Display
4.exit
Enter
your choice: 2
List is empty. Cannot delete.
