Write A Program For Insertion Of A Node In A Doubly Linked List

Program

   # include <stdio.h>
   # include <stdlib.h>
   struct dnode
   {
   int data;
   struct node *left, *right;
   };
   struct dnode *insert(struct dnode *p, struct dnode **q, int n)
   {
   struct dnode *temp;
   /* if the existing list is empty then insert a new node as the
starting node */
   if(p==NULL)
     {
         p=(struct dnode *)malloc(sizeof(struct dnode)); /* creates new
node data value
      passed as parameter */

         if(p==NULL)
         {
      printf("Error\n");
             exit(0);
         }
         p-> data = n;
         p-> left = p->right =NULL;
         *q =p
      }
      else
      {
         temp = (struct dnode *)malloc(sizeof(struct dnode)); /* creates
new node using
         data value passed as
         parameter and puts its
        address in the temp
   */
      if(temp == NULL)
      {
   printf("Error\n");
          exit(0);
      }
      temp-> data = n;
      temp->left = (*q);
      temp->right = NULL;
      (*q) = temp;
    }
      return (p);
   }
   void printfor( struct dnode *p )
   {
      printf("The data values in the list in the forward order are:\n");
      while (p!= NULL)
         {
            printf("%d\t",p-> data);
            p = p-> right;
         }
   }
   /* A function to count the number of nodes in a doubly linked list */
   int nodecount (struct dnode *p )
   {
      int count=0;
      while (p != NULL)
      {
         count ++;
         p = p->right;
      }
         return(count);
   }

   /* a function which inserts a newly created node after the specified
node in a doubly
   linked list */
struct node * newinsert ( struct dnode *p, int node_no, int value )
      {
      struct dnode *temp, * temp1;
      int i;
      if ( node_no <= 0 || node_no > nodecount (p))
      {
      printf("Error! the specified node does not exist\n");
      exit(0);
      }
      if ( node_no == 0)
      {
      temp = ( struct dnode * )malloc ( sizeof ( struct dnode ));
      if ( temp == NULL )
      {
      printf( " Cannot allocate \n");
      exit (0);
      }
      temp -> data = value;
      temp -> right = p;
      temp->left = NULL
      p = temp ;
      }
      else
      {
      temp = p ;
      i = 1;
      while ( i < node_no )
      {
      i = i+1;
      temp = temp-> right ;
      }
      temp1 = ( struct dnode * )malloc ( sizeof(struct dnode));
      if ( temp == NULL )
      {
      printf("Cannot allocate \n");
      exit(0);
      }
      temp1 -> data = value ;
      temp1 -> right = temp -> right;
      temp1 -> left = temp;
      temp1->right->left = temp1;
      temp1->left->right = temp1
      }
      return (p);
   }
   void main()
   {
         int n;
         int x;
         struct dnode *start = NULL ;
         struct dnode *end = NULL;
         printf("Enter the nodes to be created \n");
         scanf("%d",&n);
         while ( n- > 0 )
         {
      printf( "Enter the data values to be placed in a node\n");
            scanf("%d",&x);
            start = insert ( start, &end,x );
         }
         printf("The created list is\n");
         printfor ( start );
         printf("enter the node number after which the new node is to be
inserted\n");
         scanf("%d",&n);
         printf("enter the data value to be placed in the new node\n");
         scanf("%d",&x);
         start=newinsert(start,n,x);
         printfor(start);
   }