Insert at Specific Position in Doubly Linked List in DSA C - Build from Scratch

Insert at Specific Position in Doubly Linked List

📖 Scenario: You are managing a playlist of songs using a doubly linked list. Each song has a unique ID. You want to insert a new song at a specific position in the playlist.

🎯 Goal: Build a program that creates a doubly linked list with initial songs, sets the position to insert a new song, inserts the new song at that position, and then prints the updated playlist.

📋 What You'll Learn

Create a doubly linked list with exactly three nodes having song IDs 101, 102, and 103 in that order.

Create an integer variable called position and set it to 2.

Create a new node with song ID 150 and insert it at the position in the doubly linked list.

Print the updated doubly linked list from head to tail showing song IDs separated by arrows.

💡 Why This Matters

🌍 Real World

Doubly linked lists are used in music players, browsers (history navigation), and many applications where you need to move forward and backward efficiently.

💼 Career

Understanding how to insert nodes in doubly linked lists is important for software engineers working on low-level data structures, embedded systems, or performance-critical applications.

1

Create the initial doubly linked list

Create a doubly linked list with three nodes having song IDs 101, 102, and 103 in that order. Use a struct called Node with int data, Node* prev, and Node* next. Create a pointer called head pointing to the first node.

DSA C

#include 
#include 

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

int main() {
    // Create nodes and link them
    // Your code here
    return 0;
}

Hint

Remember to allocate memory for each node using malloc and link the prev and next pointers correctly.

2

Set the position to insert the new node

Create an integer variable called position and set it to 2. This means the new song will be inserted as the second node in the list.

DSA C

#include 
#include 

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

int main() {
    struct Node* head = (struct Node*)malloc(sizeof(struct Node));
    struct Node* second = (struct Node*)malloc(sizeof(struct Node));
    struct Node* third = (struct Node*)malloc(sizeof(struct Node));

    head->data = 101;
    head->prev = NULL;
    head->next = second;

    second->data = 102;
    second->prev = head;
    second->next = third;

    third->data = 103;
    third->prev = second;
    third->next = NULL;

    // Create position variable
    // Your code here
    return 0;
}

Hint

Just declare an integer variable named position and assign it the value 2.

3

Insert the new node at the specified position

Create a new node with song ID 150 and insert it at the position in the doubly linked list. Update the prev and next pointers of the surrounding nodes accordingly.

DSA C

#include 
#include 

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

int main() {
    struct Node* head = (struct Node*)malloc(sizeof(struct Node));
    struct Node* second = (struct Node*)malloc(sizeof(struct Node));
    struct Node* third = (struct Node*)malloc(sizeof(struct Node));

    head->data = 101;
    head->prev = NULL;
    head->next = second;

    second->data = 102;
    second->prev = head;
    second->next = third;

    third->data = 103;
    third->prev = second;
    third->next = NULL;

    int position = 2;

    // Insert new node at position
    // Your code here
    return 0;
}

Hint

Traverse to the node before the position, then adjust pointers to insert the new node.

4

Print the updated doubly linked list

Print the updated doubly linked list from head to the end. Display the song IDs separated by arrows like 101 <-> 150 <-> 102 <-> 103.

DSA C

#include 
#include 

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

int main() {
    struct Node* head = (struct Node*)malloc(sizeof(struct Node));
    struct Node* second = (struct Node*)malloc(sizeof(struct Node));
    struct Node* third = (struct Node*)malloc(sizeof(struct Node));

    head->data = 101;
    head->prev = NULL;
    head->next = second;

    second->data = 102;
    second->prev = head;
    second->next = third;

    third->data = 103;
    third->prev = second;
    third->next = NULL;

    int position = 2;

    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = 150;

    struct Node* temp = head;
    int i;
    for (i = 1; i next;
    }

    newNode->next = temp->next;
    newNode->prev = temp;
    if (temp->next != NULL) {
        temp->next->prev = newNode;
    }
    temp->next = newNode;

    // Print the list
    // Your code here
    return 0;
}

Hint

Use a while loop to traverse from head to the end, printing each node's data. Print arrows between nodes but not after the last node.