Like doubly link list it also contains address of next node and data but the change is that it also contains the address of previous node.

So here we have 3 block of

• Previous node address

• Data

• Next node address

We will make it using 5 function:

• Declaring a node

• Creating a node

• Inserting a data

• Printing the data

• Main function

Declaring a node

struct Node {
    int data;//new data
    struct Node* next;//address of the next node
    struct Node* prev;//address of the previous node
};

Creating a node

struct Node* createNode(int data) {
    struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
    new_node->data = data;//assigning the data of link list
    new_node->next = NULL;//addressing the node to next node.
    new_node->prev = NULL;//addressing the node to previous node.
    return new_node;
}

Inserting the data in node

void insert(struct Node** head, int new_data) {
    struct Node* new_node = createNode(new_data); //creating a newNode
    struct Node* last = *head; //Assingning the value to the last node

    if (*head == NULL) { //checking if the linked list is empty
        *head = new_node; //if empty assign the value
        return;
    }
    while (last->next != NULL) { //traversing the link list
        last = last->next;//forwarding the data of link list
    }
    last->next = new_node; 
    new_node->prev = last;
}

Here we are adding the address of last node for the link list.

Printing the linked list

// Function to print the doubly linked list
void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d <-> ", node->data);
        node = node->next;
    }
    printf("NULL\n");
}

This function is made to increase the readability of code and make it easier to understand for user.

Main function

int main() {
    struct Node* head = NULL;
    int n, value;

    printf("Enter the number of nodes: ");
    scanf("%d", &n);

    for (int i = 0; i < n; i++) {
        printf("Enter value for node %d: ", i + 1);
        scanf("%d", &value);
        insertEnd(&head, value);
    }

    printf("Original doubly linked list: ");
    printList(head);

    return 0;
}

In this code we are calling the function and getting the values from users that we have to use.

Complete code

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

struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};

struct Node* createNode(int data) {
    struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
    new_node->data = data;
    new_node->next = NULL;
    new_node->prev = NULL;
    return new_node;
}

void insertEnd(struct Node** head, int new_data) {
    struct Node* new_node = createNode(new_data);
    struct Node* last = *head;

    if (*head == NULL) {
        *head = new_node;
        return;
    }

    while (last->next != NULL) {
        last = last->next;
    }

    last->next = new_node;
    new_node->prev = last;
}

void printList(struct Node* node) {
    while (node != NULL) {
        printf("%d <-> ", node->data);
        node = node->next;
    }
    printf("NULL\n");
}

int main() {
    struct Node* head = NULL;
    int n, value;
    printf("Enter the number of nodes: ");
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        printf("Enter value for node %d: ", i + 1);
        scanf("%d", &value);
        insertEnd(&head, value);
    }   
    printf("Original doubly linked list: ");
    printList(head);

    return 0;
}

There are many more ways we can use doubly link list.

Questions for doubly link list are:

• Traversal Doubly Link List

• Reversal of Doubly Link List

• Merge to link list

• Deleting the value of doubly link list etc.