WAP to implement the concept of linked list.

# include <stdio.h>
# include <malloc.h>

struct node
{
int info;
struct node *link;
}*start;

main()
{
int choice,n,m,position,i;
start=NULL;
while(1)
{
printf("1.Create List\n");
printf("2.Add at begining\n");
printf("3.Add after \n");
printf("4.Delete\n");
printf("5.Display\n");
printf("6.Count\n");
printf("7.Reverse\n");
printf("8.Search\n");
printf("9.Quit\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("How many nodes you want : ");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("Enter the element : ");
scanf("%d",&m);
create_list(m);
}
break;
case 2:
printf("Enter the element : ");
scanf("%d",&m);
addatbeg(m);
break;
case 3:
printf("Enter the element : ");
scanf("%d",&m);
printf("Enter the position after which this element is inserted : ");
scanf("%d",&position);
addafter(m,position);
break;
case 4:
if(start==NULL)
{
printf("List is empty\n");
continue;
}
printf("Enter the element for deletion : ");
scanf("%d",&m);
del(m);
break;
case 5:
display();
break;
case 6:
count();
break;
case 7:
rev();
break;
case 8:
printf("Enter the element to be searched : ");
scanf("%d",&m);
search(m);
break;
case 9:
exit();
default:
printf("Wrong choice\n");
}/*End of switch */
}/*End of while */
}/*End of main()*/

create_list(int data)
{
struct node *q,*tmp;
tmp= malloc(sizeof(struct node));
tmp->info=data;
tmp->link=NULL;

if(start==NULL) /*If list is empty */
start=tmp;
else
{       /*Element inserted at the end */
q=start;
while(q->link!=NULL)
q=q->link;
q->link=tmp;
}
}/*End of create_list()*/

addatbeg(int data)
{
struct node *tmp;
tmp=malloc(sizeof(struct node));
tmp->info=data;
tmp->link=start;
start=tmp;
}/*End of addatbeg()*/

addafter(int data,int pos)
{
struct node *tmp,*q;
int i;
q=start;
for(i=0;i<pos-1;i++)
{
q=q->link;
if(q==NULL)
{
printf("There are less than %d elements",pos);
return;
}
}/*End of for*/

tmp=malloc(sizeof(struct node) );
tmp->link=q->link;
tmp->info=data;
q->link=tmp;
}/*End of addafter()*/

del(int data)
{
struct node *tmp,*q;
if(start->info == data)
{
tmp=start;
start=start->link;  /*First element deleted*/
free(tmp);
return;
}
q=start;
while(q->link->link != NULL)
{
if(q->link->info==data)     /*Element deleted in between*/
{
tmp=q->link;
q->link=tmp->link;
free(tmp);
return;
}
q=q->link;
}/*End of while */
if(q->link->info==data)    /*Last element deleted*/
{
tmp=q->link;
free(tmp);
q->link=NULL;
return;
}
printf("Element %d not found\n",data);
}/*End of del()*/

display()
{
struct node *q;
if(start == NULL)
{
printf("List is empty\n");
return;
}
q=start;
printf("List is :\n");
while(q!=NULL)
{
printf("%d ", q->info);
q=q->link;
}
printf("\n");
}/*End of display() */

count()
{
struct node *q=start;
int cnt=0;
while(q!=NULL)
{
q=q->link;
cnt++;
}
printf("Number of elements are %d\n",cnt);
}/*End of count() */

rev()
{
struct node *p1,*p2,*p3;
if(start->link==NULL)    /*only one element*/
return;
p1=start;
p2=p1->link;
p3=p2->link;
p1->link=NULL;
p2->link=p1;
while(p3!=NULL)
{
p1=p2;
p2=p3;
p3=p3->link;
p2->link=p1;
}
start=p2;
}/*End of rev()*/

search(int data)
{
struct node *ptr = start;
int pos = 1;
while(ptr!=NULL)
{
if(ptr->info==data)
{
printf("Item %d found at position %d\n",data,pos);
return;
}
ptr = ptr->link;
pos++;
}
if(ptr == NULL)
printf("Item %d not found in list\n",data);
}/*End of search()*/