Insertion in Double Linked list

 

#include <stdio.h>

#include<stdlib.h>

struct node{

    int data;

    struct node *prev;

    struct node *link;

};

void display(struct node *ptr){

    while(ptr!=NULL){

        printf(" %d ",ptr->data);

        ptr = ptr->link;

    }

}

struct node *insert_beg(struct node *head, int s){

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

    head->prev = e;

    e->link = head;

    e->data = s;

   

return  e;

}

struct node *insert_end(struct node *head,int s){

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

    struct node *ptr = head;

   e->data =s;

   e->link = NULL;    

   e->prev = NULL;

   while(ptr->link!=NULL)

   {

       ptr= ptr->link;

   }

   ptr->link = e;

   e->prev = ptr;

   return head;  

}

struct node *insert_pos(struct node *head,int s,int pos){

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

    struct node *ptr = head;

    int j = 0;

    while (j!=pos-1)

    {

        ptr= ptr->link;

        j++;

    }

    e->data = s;

    e->link = ptr->link;

    e->prev = ptr;

    ptr->link = e;

return head;

   

}

int main()

{

    struct node *a;

    struct node *b;

    struct node *c;

    struct node *d;

 

   

    a = malloc(sizeof(struct node));

    b = malloc(sizeof(struct node));

    c = malloc(sizeof(struct node));

    d = malloc(sizeof(struct node));

   

    a->prev = NULL;

    a->data = 1;

    a->link = b;

    b->prev = a;

    b->data = 2;

    b->link = c;

    c->prev = b;

    c->data = 3;

    c->link = d;

    d->prev = c;

    d->data = 4;

    d->link = NULL;

display(a);

printf("\n");

// a = insert_beg(a,0);

// a = insert_end(a,5);

a = insert_pos(a,0,1);

display(a);

   

    return 0;

}