#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data; // The data contained in this node
    struct Node* prev; // A pointer to the previous node in the list
    struct Node* next; // A pointer to the next node in the list
};

void display_traversal_forward(struct Node* node)
{
    printf("Linked List: ");
    
    // as linked list will end when Node is Null
    while( node != NULL ){
        printf("%d ",node -> data);
        node = node -> next;
    }
    
    printf("\n");
}

void display_traversal_backward(struct Node* node)
{
    printf("Linked List: ");
    
    // as linked list will end when Node is Null
    while( node != NULL ){
        printf("%d ",node -> data);
        node = node -> prev;
    }
    
    printf("\n");
}

int main() {
    // Creating the Nodes
    struct Node* first;
    struct Node* second;
    struct Node* third;
    struct Node* fourth;

    first = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));
    fourth = (struct Node*)malloc(sizeof(struct Node));

    first -> data = 10; 
    second -> data = 20;
    third -> data = 30;
    fourth -> data = 40;

    first -> next = second;
    second -> next = third;
    third -> next = fourth;
    fourth -> next = NULL;

    first -> prev = NULL;
    second -> prev = first;
    third -> prev = second;
    fourth -> prev = third;

    // Traversing the nodes

    display_traversal_forward(first);
    display_traversal_backward(fourth);

    return 0;
}