Insert at End of Doubly Linked List in DSA C - Build from Scratch

Insert at End of Doubly Linked List

📖 Scenario: You are building a simple program to manage a list of tasks. Each task is stored in a doubly linked list node. You want to add new tasks to the end of the list.

🎯 Goal: Learn how to insert a new node at the end of a doubly linked list and print the list from start to end.

📋 What You'll Learn

Create a doubly linked list node structure with data, prev, and next pointers.

Initialize an empty doubly linked list with a head pointer.

Write a function to insert a new node at the end of the doubly linked list.

Write a function to print the doubly linked list from head to end.

💡 Why This Matters

🌍 Real World

Doubly linked lists are used in many applications like browser history, music playlists, and undo-redo features where you need to move forward and backward easily.

💼 Career

Understanding linked lists is fundamental for software developers, especially for roles involving system programming, embedded systems, or any application requiring efficient dynamic data management.

1

Create the doubly linked list node and initialize head

Define a struct called Node with an int data, a Node* called prev, and a Node* called next. Then create a Node* variable called head and set it to NULL.

DSA C

# Define the Node struct and initialize head
// Your code here

Hint

Use typedef struct Node to define the node. Initialize head as NULL to show the list is empty.

2

Create a function to insert a new node at the end

Write a function called insertAtEnd that takes an int data parameter. Inside, create a new Node* called newNode using malloc. Set newNode->data to data, and both newNode->prev and newNode->next to NULL. If head is NULL, set head to newNode. Otherwise, traverse the list to find the last node, then set its next to newNode and newNode->prev to that last node.

DSA C

#include 
#include 

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

Node* head = NULL;

// Write insertAtEnd function here
// Your code here

Hint

Remember to handle the empty list case by setting head to the new node. Otherwise, find the last node and link the new node after it.

3

Create a function to print the doubly linked list

Write a function called printList that starts from head and uses a while loop to print each node's data followed by -> . Stop when the current node is NULL. After the loop, print NULL.

DSA C

#include 
#include 

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

Node* head = NULL;

void insertAtEnd(int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;

    if (head == NULL) {
        head = newNode;
        return;
    }

    Node* temp = head;
    while (temp->next != NULL) {
        temp = temp->next;
    }

    temp->next = newNode;
    newNode->prev = temp;
}

// Write printList function here
// Your code here

Hint

Use a temporary pointer to walk through the list from head to NULL. Print each node's data followed by an arrow.

4

Insert nodes and print the list

Call insertAtEnd three times to add nodes with data 10, 20, and 30. Then call printList() to display the list.

DSA C

#include 
#include 

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

Node* head = NULL;

void insertAtEnd(int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;

    if (head == NULL) {
        head = newNode;
        return;
    }

    Node* temp = head;
    while (temp->next != NULL) {
        temp = temp->next;
    }

    temp->next = newNode;
    newNode->prev = temp;
}

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

// Insert nodes and print the list
// Your code here

Hint

Call insertAtEnd with 10, 20, and 30. Then call printList() to see the list.