Doubly linked list.c

#include <stdio.h>
#include <stdlib.h>
struct node {
    int data;
    struct node * prev;
    struct node * next;
}*head, *last;
void createList(int n)
{   int i, data;
    struct node *newNode;
    if(n >= 1)
    {   head = (struct node *)malloc(sizeof(struct node));
        printf("Enter data of 1 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("Enter data of %d node: ", 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("DATA of %d node = %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");
    }
}
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("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");
    }
    return 0;
}