C program to insert delete and display using doubly linked list...

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#include <stdio.h>
#include <stdlib.h>
struct node
{
  int item;
  struct node *prev;
  struct node *next;
};
struct node *head = NULL;
struct node *start = NULL;
struct node *
create_new_node ()
{
  struct node *temp = (struct node *) malloc (sizeof (struct node));


  if (!temp)
    {
      printf (" memory not allocated ..exiting...\n");
      getchar ();
      exit (1);
    }
  return temp;
}

void
insert (int x)
{
  struct node *var = create_new_node ();

  var->item = x;
  var->next = NULL;
  if (start == NULL && head == NULL)
    {
      var->prev = NULL;
      head = start = var;
    }
  else
    {
      var->prev = head;
      head->next = var;
      head = var;
    }

}

void
display (struct node *start)
{
  struct node *temp;
  temp = start;
  if (temp == NULL)
    return;
  else
    {
      while (temp != NULL)
{
  printf ("%d ->", temp->item);
  temp = temp->next;

}

    }
}

void
ldelete (int x, struct node *start)
{
  struct node *temp = start;
  struct node *temp2;
  while (temp != NULL)
    {
      if (temp->item == x)

{
  if (temp->prev == NULL)
    start = temp->next;
  else if (temp->next == NULL)
    (temp->prev)->next = NULL;
  else
    {
      temp2 = temp->prev;
      temp2->next = temp->next;
    }
  free (temp);
  return;
}



      temp = temp->next;
    }
  printf ("no such data exist\n");
  return;
}







void
main ()
{
  int i, choice;
  system ("clear");
  do
    {
      printf
("\n\nEnter 1 to insert and 2 to display  3 to delete 4 to exit\n\n");
      scanf ("%d", &choice);
      if (choice == 1)
{
  printf ("Enter data element to be inserted\n");
  scanf ("%d", &i);
  insert (i);
}
      else if (choice == 2)
{
  display (start);
}
      else if (choice == 3)
{
  printf ("Enter data to be deleted\n");
  scanf ("%d", &i);
  ldelete (i, start);
}


    }
  while (choice != 4);
}