Write a program to operate on linked list.All possible operation are performed through separate functions.

#include<stdio.h>
#include<malloc.h>
struct node
{
int data;
struct node *next;
};
struct node *start=NULL;
struct node *create_11(struct node *);
struct node *display(struct node *);
struct node *insert_beg(struct node *);
struct node *insert_end(struct node *);
struct node *insert_before(struct node *);
struct node *insert_after(struct node *);
struct node *delete_beg(struct node *);
struct node *delete_end(struct node *);
struct node *delete_node(struct node *);
struct node *delete_after(struct node *);
struct node *delete_list(struct node *);
struct node *sort_list(struct node *);
int main()
{
int option;
do
{
printf("\n\n *****MAIN MENU*****");
printf("\n1:Create a list");
printf("\n2:Display the list");
printf("\n3:Add a node at the beginning");
printf("\n4:Add a node at the end");
printf("\n5:Add a before a given node");
printf("\n6:Add a node after a given node");
printf("\n7:Delete from the beginning");
printf("\n8:Delete from the end");
printf("\n9:Delete a given node");
printf("\n10:Delete after a given node");
printf("\n11:Delete the entire list");
printf("\n12:Sort the list");
printf("\n13:EXIT");
printf("\n***********************");
printf("\n\n Enter your option:");
scanf("%d",&option);
switch(option)
{
case 1:
start=create_11(start);
printf("\n LINKED LIST CREATED");
break;
case 2:
start=display(start);
break;
case 3:
start=insert_beg(start);
break;
case 4:
start=insert_end(start);
break;
case 5:
start=insert_before(start);
break;
case 6:
start=insert_after(start);
break;
case 7:
start=delete_beg(start);
break;
case 8:
start=delete_end(start);
break;
case 9:
start=delete_node(start);
break;
case 10:
start=delete_after(start);
break;
case 11:
start=delete_list(start);
printf("\n LINKED LAST DELETED");
break;
case 12:
start=sort_list(start);
break;
}
}while(option !=13);
getch();
return 0;
}
struct node *create_11(struct node *start)
{
struct node *new_node,*ptr;
int num;
printf("\n Enter -1 to end");
printf("\n Enter the data:");
scanf("%d",&num);
while(num!=-1)
{
new_node=(struct node*)
malloc(sizeof(struct node));
new_node->data=num;
if(start==NULL)
{
new_node->next=NULL;
start=new_node;
}
else
{
ptr=start;
while(ptr->next!=NULL)
ptr=ptr->next;
ptr->next=new_node;
new_node->next=NULL;
}
printf("\n ENTER THE DATA");
scanf("%d",&num);
}
return start;
}
struct node *display(struct node *start)
{
struct node *ptr;
ptr = start;
while(ptr!=NULL)
{
printf("\t %d",ptr->data);
ptr=ptr->next;
}
return start;
 }
 struct node *insert_beg(struct node *start)
 {
  struct node *new_node;
  int num;
  printf("\n Enter the data");
  scanf("%d",&num);
  new_node= (struct node *)
malloc(sizeof(struct node));
  new_node->next=start;
  start=new_node;
  return start;
 }
 struct node *insert_end(struct node *start)
 {
  struct node *ptr, *new_node;
  int num;
  printf("\n Enter the data:");
  scanf("%d",&num);
  new_node=(struct node *)
malloc(sizeof(struct node));
new_node->data=num;
new_node->next=NULL;
ptr=start;
while(ptr->next!=NULL)
ptr=ptr->next;
ptr->next=new_node;
return start;
 }
 struct node *insert_before(struct node *start)
{
struct node *new_node, *ptr, *preptr;
int num, val;
printf("\n Enter the data");
scanf("%d",&num);
printf("\n Enter the value before which the data has to be inserted:");
scanf("%d",&val);
new_node=(struct node *)
malloc(sizeof(struct node));
new_node->data=num;
ptr=start;
while(ptr->data!=val)
{
preptr=ptr;
ptr=ptr->next;
}
preptr->next=new_node;
new_node->next = ptr;
return start;
}
struct node *insert_after(struct node *start)
{
struct node *new_node, *ptr, *preptr;
int num,val;
printf("\n Enter the data:");
scanf("%d",&num);
printf("\n Enter the value after which the data has to be inserted");
scanf("%d",&val);
new_node=(struct node *)
malloc(sizeof(struct node));
new_node->data=num;
ptr=start;
preptr = ptr;
while(preptr->data !=val)
{
preptr=ptr;
ptr=ptr->next;
}
preptr->next=new_node;
new_node->next=ptr;
return start;
}
struct node *delete_beg(struct node *start)
{
struct node *ptr;
ptr = start;
start = start->next;
free(ptr);
return start;
}
struct node *delete_end(struct node *start)
{
struct node *ptr, *preptr;
ptr = start;
while(ptr->next!=NULL)
{
preptr = ptr;
ptr = ptr->next;
}
preptr->next = NULL;
free(ptr);
return start;
}
struct node *delete_node(struct node *start)
{
struct node *ptr, *preptr;
int val;
printf("\n Enter the value of the node which has to be deleted");
scanf("%d", &val);
ptr=start;
if(ptr->data==val)
{
start=delete_beg(start);
return start;
}
else
{
while(ptr->data!=val)
{
preptr=ptr;
ptr=ptr->next;
}
preptr->next=ptr->next;
free(ptr);
return start;
}
}
struct node *delete_after(struct node *start)
{
struct node *ptr,*preptr;
int val;
printf("\n Enter the value after which the node has to be deleted");
scanf("%d",&val);
ptr=start;
while(preptr->data!=val)
{
preptr = ptr;
ptr=ptr->next;
}
preptr->next=ptr->next;
free(ptr);
return start;
}
struct node *delete_list(struct node *start)
{
struct node *ptr;
ptr=start;
while(ptr->next!=NULL)
{
printf("\n %d is to be deleted next",ptr->data);
start=delete_beg(ptr);
ptr=ptr->next;
}
return start;
}
struct node *sort_list(struct node *start)
{
struct node *ptr1, *ptr2;
int temp;
ptr1=start;
while(ptr1->next!=NULL)
{
ptr2=ptr1->next;
while(ptr2!=NULL)
{
if(ptr1->data>ptr2->data)
{
temp=ptr1->data;
ptr1->data=ptr2->data;
ptr2->data=temp;
}
ptr2=ptr2->next;
}
ptr1=ptr1->next;
}
return start;
}