#include <stdio.h>
#include <stdlib.h>
 
// Structure definition
struct Node {
    int data;
    struct Node *prev;
    struct Node *next;
};
 
// Function to create a new node
struct Node* createNode(int data) {
    struct Node *newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}
 
// Function to insert at end
struct Node* insertAtEnd(struct Node *head, int data) {
    struct Node *newNode = createNode(data);
    if (head == NULL)
        return newNode;
 
    struct Node *temp = head;
    while (temp->next != NULL)
        temp = temp->next;
 
    temp->next = newNode;
    newNode->prev = temp;
    return head;
}
 
// Function to display list
void displayList(struct Node *head) {
    struct Node *temp = head;
    printf("\nDoubly Linked List: ");
    while (temp != NULL) {
        printf("%d <-> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}
 
// Function to reverse the doubly linked list
struct Node* reverseList(struct Node *head) {
    struct Node *temp = NULL;
    struct Node *current = head;
 
    if (head == NULL) {
        printf("\nList is empty.\n");
        return NULL;
    }
 
    // Swap next and prev for all nodes
    while (current != NULL) {
        temp = current->prev;
        current->prev = current->next;
        current->next = temp;
        current = current->prev; // move to the next node (previous before swap)
    }
 
    // Adjust head pointer
    if (temp != NULL)
        head = temp->prev;
 
    printf("\nList has been reversed.\n");
    return head;
}
 
int main() {
    struct Node *head = NULL;
    int n, data, i;
 
    printf("Enter number of nodes: ");
    scanf("%d", &n);
 
    for (i = 1; i <= n; i++) {
        printf("Enter data for node %d: ", i);
        scanf("%d", &data);
        head = insertAtEnd(head, data);
    }
 
    displayList(head);
 
    head = reverseList(head);
 
    displayList(head);
 
    return 0;
}