C program to implement Circular Linklist

C program to implement Circular Linklist

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<alloc.h>
#define null 0
struct node
{
 int info;
 struct node *link;
}*start;

void main()
{
 int ch,n,m,position,i;
 last=null;
 while(1)
 {
  printf("1.create 
   2.addat
   3.addbt
   4.del
   5.disp
   6.exit
  ");
  printf("er ur ch");
  scanf("%d",&ch);
  switch(ch)
  {
   case 1:
   printf("er no of itc");
   scanf("%d",&n);
   for(i=0;i<n;i++)
   {
    printf("er the element");
    scanf("%d",&m);
    create(m);
   }
   break;
 
   case 2:
   printf("er the element");
   scanf("%d",&m);
   addat(m);
   break;
 
   case 3:
   printf("er the element");
   scanf("%d",&m);

   printf("er the position");
   scanf("%d",&position);
   addbt(m,position);
   break;
   
   case 4:
   if(last==null)
   {
    printf("list is empty");
    continue;
   }
   printf("er the element for delete");
   scanf("%d",&m);
   del(m);
   break;
 
   case 5:
   disp();
   break;
 
   case 6:
   exit(0);
   break;
 
   default:
   printf("wrong choice");
  }
 }
}
 
create(int data)
{
 struct node *q,*tmp;
 tmp=(struct node  *)malloc(sizeof(struct node));
 tmp->info=data;
 tmp->link=null;
 if(last==null)
 {
  last=tmp;
  tmp->link=last;
 }
 else
 {
  tmp->link=last->link;
  last->link=tmp;
  last=tmp;
 }
}


addat(int data)
{

 struct node *q,*tmp;
 tmp=(struct node  *)malloc(sizeof(struct node));
 tmp->info=data;
 tmp->link=last->link;
 last->link=tmp;
}

addbt(int data,int pos)
{
 struct node *tmp,*q;
 int i;
 q=last->link;;
 for(i=0;i<pos-1;i++)
 {
  q=q->link;
  if(q==last->link)
  {
   printf("there r lessthan %d elements",pos);
   return;
  }
 }
 tmp=(struct node  *)malloc(sizeof(struct node));
 tmp->link=q->link;
 tmp->info=data;
 q->link=tmp;
 if(q==last)
 last=tmp;
}

del(int data)
{
 struct node *tmp,*q;
 if(last->link==last&&last->info==data)
 {
  tmp=last;
  last=null;
  free(tmp);
  return;
 }
 q=last->link;
 if(q->info==data)
 {
  tmp=q;
  last->link=q->link;
  free(tmp);
  return;
 }
 while(q->link!=last)
 {
  if(q->link->info==data)
  {
   tmp=q->link;
   q->link=tmp->link;
   free(tmp);
   printf("element %d is deleted",data);
  }
  if(q->link->info=data)
  {
   tmp=q->link;
   q->link=last->link;
   free(tmp);
   last=q;
   return;}
   printf("element%d is not found",data);
  }
 }
}

disp()
{
 struct node *q;
 if(last==null)
 {
 printf("list isdempty");
 return;
 }q=last->link;
 while(q!=last)
 {
  printf("%d",q->info);
  q=q->link;
 }
 printf("%d",last->info);
}