Circular linked list

/*

Write a program fro circular linked list

*/

#include<stdio.h>
#include<stdlib.h>

struct node

{

int info;

struct node *link;

};

struct node *create_list(struct node *last);

void display(struct node *last);

struct node *addtoempty(struct node *last,int data);

struct node *addatbeg(struct node *last,int data);

struct node *addatend(struct node *last,int data);

struct node *addafter(struct node *last,int data,int item);

struct node *del(struct node *last,int data);

main( )

{

int choice,data,item;

struct node *last=NULL;

while(1)

{

printf("1.Create List\n");

printf("2.Display\n");

printf("3.Add to empty list\n");

printf("4.Add at beginning\n");

printf("5.Add at end\n");

printf("6.Add after \n");

printf("7.Delete\n");

printf("8.Quit\n");

printf("Enter your choice : ");

scanf("%d",&choice);

switch(choice)

{

case 1:

last=create_list(last);

break;

case 2:

display(last);

break;

case 3:

printf("Enter the element to be inserted : ");

scanf("%d",&data);

last=addtoempty(last,data);

break;

case 4:

printf("Enter the element to be inserted : ");

scanf("%d",&data);

last=addatbeg(last,data);

break;

case 5:

printf("Enter the element to be inserted : ");

scanf("%d",&data);

last=addatend(last,data);

break;

case 6:

printf("Enter the element to be inserted : ");

scanf("%d",&data);

printf("Enter the element after which to insert : ");

scanf("%d",&item);

last=addafter(last,data,item);

break;

case 7:

printf("Enter the element to be deleted : ");

scanf("%d",&data);

last=del(last,data);

break;

case 8:

exit(1);

default:

printf("Wrong choice\n");

}
}
}

struct node *create_list(struct node *last)

{

int i,n,data;

printf("Enter the number of nodes : ");

scanf("%d",&n);

last=NULL;

if(n==0)

return last;

printf("Enter the element to be inserted : ");

scanf("%d",&data);

last=addtoempty(last,data);


for(i=2;i<=n;i++)

{

printf("Enter the element to be inserted : ");

scanf("%d",&data);

last=addatend(last,data);

}

return last;

}

struct node *addtoempty(struct node *last,int data)

{

struct node *tmp;

tmp=(struct node *)malloc(sizeof(struct node));

tmp->info=data;

last=tmp;

last->link=last;

return last;

}

struct node *addatbeg(struct node *last,int data)

{

struct node *tmp;

tmp=(struct node *)malloc(sizeof(struct node));

tmp->info=data;

tmp->link=last->link;

last->link=tmp;

return last;

}

struct node *addatend(struct node *last,int data)

{

struct node *tmp;

tmp=(struct node *)malloc(sizeof(struct node));

tmp->info=data;

tmp->link=last->link;

last->link=tmp;

last=tmp;

return last;

}

struct node *addafter(struct node *last,int data,int item)

{

struct node *tmp,*p;

p=last->link;

do

{

if(p->info==item)

{

tmp=(struct node *)malloc(sizeof(struct node));

tmp->info=data;

tmp->link=p->link;

p->link=tmp;

if(p==last)

last=tmp;

return last;

}

p=p->link;

}while(p!=last->link);

printf("%d not present in the list\n",item);

return last;

}


struct node *del(struct node *last,int data)

{

struct node *tmp,*p;

if(last==NULL)

{

printf("List is empty\n");

return last;

}

/*Deletion of only node*/

if(last->link==last && last->info==data)

{

tmp=last;

last=NULL;

free(tmp);

return last;

}

/*Deletion of first node*/

if(last->link->info==data)

{

tmp=last->link;

last->link=tmp->link;

free(tmp);

return last;

}

/*Deletion in between*/

p=last->link;

while(p->link!=last)

{

if(p->link->info==data)

{

tmp=p->link;

p->link=tmp->link;

free(tmp);

return last;

}

p=p->link;

}

/*Deletion of last node*/

if(last->info==data)

{

tmp=last;

p->link=last->link;

last=p;

free(tmp);

return last;

}

printf("Element %d not found\n",data);

return last;

}


void display(struct node *last)

{

struct node *p;

if(last==NULL)

{

printf("List is empty\n");

return;

}

p=last->link;

do

{

printf("%d ",p->info);

p=p->link;

}while(p!=last->link);

printf("\n");

}