#include <stdio.h>
#include <stdlib.h>
typedef struct node
{
    int data;
    struct node* next;
    struct node* prev;
}node;

node* start;

void insert()
{
    node *ptr, *temp;
    int val, loc, i;
    ptr=(node *)malloc(sizeof(node));

    if(ptr==NULL)
    {
        printf("Overflow!\n");
        return;
    }

    temp=start;
    printf("Enter location\n");
    scanf("%d", &loc);

    for(i=0; i<loc; i++)
    {
        temp=temp->next;
        if(temp==NULL)
        {
            printf("There are less than %d elements in list\n", loc);
            return;
        }
    }

    printf("Enter value to be entered\n");
    scanf("%d", &val);

    ptr->data=val;
    ptr->next=temp->next;
    ptr->prev=temp;
    temp->next=ptr;
    temp->next->prev=ptr;
    printf("Element %d added successfully at %d position", val, loc);

}

void delete()
{
    node *ptr, *temp;
    ptr=start;
    if(ptr==NULL)
    {
        printf("Underflow\n");
        return;
    }
    int val;
    printf("Enter the value after which element has to be deleted\n");
    scanf("%d", &val);

    while(ptr->data!=val)
    ptr=ptr->next;

    if(ptr->next=NULL)
    printf("Can't delete\n");

    else if(ptr->next->next==NULL)
    {
        ptr->next=NULL;
        printf("Node deleted\n");
    }

    else
    {
        temp=ptr->next;
        ptr->next=temp->next;
        temp->next->prev=ptr;
        free(temp);
        printf("Node deleted\n");
    }
}

void display()
{
   node *ptr;
   ptr=start;
   while(ptr!=NULL)
   {
     printf("%d ", ptr->data);
     ptr=ptr->next;
   }

   if(ptr==NULL)
   {
    printf("List is empty\n");
   }
}

void main()
{
    int a;
    do
    {
        printf("\nEnter 1 for insert, 2 for delete, 3 for display and 4 for exit\n");
        scanf("%d", &a);
        switch(a)
        {
            case 1 : insert();
                     break;
            case 2 : delete();
                     break;
            case 3 : display();
                     break;
            case 4 : printf("Program terminated successfully\n");
                     break;
            default : printf("Enter valid inputs\n");
                      break;
        }
    }
    while(a!=4);
}