Doubly link list.c

#include <stdio.h>
#include <stdlib.h>
 struct node {
    int data;
    struct node * prev;
    struct node * next;
}*head, *last;
 void createList(int n);
void displayList();
void insertAtBeginning(int data);
void insertAtEnd(int data);
void insertAtN(int data, int position);
 int main()
{
    int n, data, choice=1;
     head = NULL;
    last = NULL;
     while(choice != 0)
    {
        
       
        printf("1. Create List\n");
        printf("2. Insert node - at beginning\n");
        printf("3. Insert node - at end\n");
        printf("4. Insert node - at N\n");
        printf("5. Display list\n");
        printf("0. Exit\n");
        printf("--------------------------------------------\n");
        printf("Enter your choice : ");
         scanf("%d", &choice);
        
        switch(choice)
        {
            case 1:
                printf("Enter the total number of nodes in list: ");
                scanf("%d", &n);
                 createList(n);
                break;
            case 2:
                printf("Enter data of first node : ");
                scanf("%d", &data);
                 insertAtBeginning(data);
                break;
            case 3:
                printf("Enter data of last node : ");
                scanf("%d", &data);
                 insertAtEnd(data);
                break;
            case 4:
                printf("Enter the position where you want to insert new node: ");
                scanf("%d", &n);
                printf("Enter data of %d node : ", n);
                scanf("%d", &data);
                 insertAtN(data, n);
                break;
            case 5:
                displayList();
                break;
            case 0:
                break;
            default:
                printf("Error! Invalid choice. Please choose between 0-5");
        }
         printf("\n\n\n\n\n");
    }
     return 0;
}
 void createList(int n)
{
    int i, data;
    struct node *newNode;
     if(n >= 1)
    {
       
        head = (struct node *)malloc(sizeof(struct node));
         
        scanf("%d", &data);
         head->data = data;
        head->prev = NULL;
        head->next = NULL;
         last = head;
         
        for(i=2; i<=n; i++)
        {
            newNode = (struct node *)malloc(sizeof(struct node));
             printf(" %d ", i);
            scanf("%d", &data);
             newNode->data = data;
            newNode->prev = last; 
            newNode->next = NULL;
             last->next = newNode; 
            last = newNode;       
        }
         printf("\nDOUBLY LINKED LIST CREATED SUCCESSFULLY\n");
    }
}
 void displayList()
{
    struct node * temp;
    int n = 1;
     if(head == NULL)
    {
        printf("List is empty.\n");
    }
    else
    {
        temp = head;
        printf("DATA IN THE LIST:\n");
         while(temp != NULL)
        {
            printf("%d\n", n, temp->data);
             n++;
          
            temp = temp->next;
        }
    }
}
 void insertAtBeginning(int data)
{
    struct node * newNode;
     if(head == NULL)
    {
        printf("Error, List is Empty!\n");
    }
    else
    {
        newNode = (struct node *)malloc(sizeof(struct node));
         newNode->data = data;
        newNode->next = head; 
        newNode->prev = NULL; 
         
        head->prev = newNode;
         
        head = newNode;
         printf("NODE INSERTED SUCCESSFULLY AT THE BEGINNING OF THE LIST\n");
    }
}
 void insertAtEnd(int data)
{
    struct node * newNode;
     if(last == NULL)
    {
        printf("Error, List is empty!\n");
    }
    else
    {
        newNode = (struct node *)malloc(sizeof(struct node));
         newNode->data = data;
        newNode->next = NULL;
        newNode->prev = last;
         last->next = newNode;
        last = newNode;
         printf("NODE INSERTED SUCCESSFULLY AT THE END OF LIST\n");
    }
}
 void insertAtN(int data, int position)
{
    int i;
    struct node * newNode, *temp;
     if(head == NULL)
    {
        printf("Error, List is empty!\n");
    }
    else
    {
        temp = head;
        i=1;
         while(i<position-1 && temp!=NULL)
        {
            temp = temp->next;
            i++;
        }
         if(position == 1)
        {
            insertAtBeginning(data);
        }
        else if(temp == last)
        {
            insertAtEnd(data);
        }
        else if(temp!=NULL)
        {
            newNode = (struct node *)malloc(sizeof(struct node));
             newNode->data = data;
            newNode->next = temp->next; 
            newNode->prev = temp;          
             if(temp->next != NULL)
            {
               
                temp->next->prev = newNode;
            }
            
            temp->next = newNode;
             printf("NODE INSERTED SUCCESSFULLY AT %d POSITION\n", position);
        }
        else
        {
            printf("Error, Invalid position\n");
        }
    }
}