🔗 Doubly Linked Lists: Easy Guide for Beginners

📌 Introduction

After learning about Singly Linked Lists, the next step in mastering data structures is understanding Doubly Linked Lists (DLLs). They offer more flexibility and bidirectional traversal — making them ideal for certain advanced applications.

In this blog, you’ll learn what a Doubly Linked List is, how it works, and how to implement one in your own programs.

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🔍 What is a Doubly Linked List?

A Doubly Linked List is a type of linked list where each node points to both its previous and next node. This allows movement in both directions — forward and backward.

Each node contains:

• Data

• Pointer to the Previous Node (prev)

• Pointer to the Next Node (next)

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🔄 Doubly vs Singly Linked List

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💻 Implementation (C++ Code Example)

#include <iostream>
using namespace std;

class Node {
public:
    int data;
    Node* prev;
    Node* next;

    Node(int value) {
        data = value;
        prev = nullptr;
        next = nullptr;
    }
};

void printForward(Node* head) {
    while (head != nullptr) {
        cout << head->data << " <-> ";
        head = head->next;
    }
    cout << "NULL" << endl;
}

int main() {
    Node* head = new Node(10);
    Node* second = new Node(20);
    Node* third = new Node(30);

    head->next = second;
    second->prev = head;

    second->next = third;
    third->prev = second;

    printForward(head);

    return 0;
}

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🔧 Common Operations in DLL

• Insert at Head / Tail

• Delete from Head / Tail

• Insert after a Node

• Reverse Traversal

• Doubly Linked List Traversal in Both Directions

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📈 Applications of Doubly Linked Lists

• Browser History (Back/Forward Navigation)

• Music Playlist Management

• Undo/Redo Systems

• Cache Implementation (LRU Cache)

• Circular Doubly Linked Lists (for round-robin scheduling)

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⚠️ Limitations

• Slightly more memory usage due to two pointers

• More complex implementation compared to singly linked list

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💡 Tip for Interview Prep

Practice these:

• Reverse a doubly linked list

• Insert/Delete at specific positions

• Detect and remove duplicate elements

• Convert DLL to Binary Tree or vice versa

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✅ Conclusion

Doubly Linked Lists offer flexibility and bidirectional control. Understanding them brings you one step closer to mastering advanced data structures like Trees, Graphs, and Deques.

Article 3: Circular Linked Lists Made Simple