Find length of Doubly Linked List

Last Updated: 20 October, 2024 🕓 3 Mins

In this article, we will learn how to find the length of a doubly linked list. Actually finding length means we will count the total number of nodes present in a doubly linked list.

To count the node, we will traverse the doubly linked list till the end node.

For Example:

As given in the diagram, there are a total 3 nodes, so we can say that the length of a doubly linked is 3.

Algorithm:

Initialize the variable count = 0

Continue to the next node until the doubly linked list nodes are exhausted.

As we move to the next node, continue to increase the count variable by 1.

Once the nodes are exhausted, return the count variable.

Example: Find the length of Doubly Linked List in Java

  
  // Class representing a node in a doubly linked list
  class Node {
    public int data;    // Data stored in the node
    public Node prev;   // Reference to the next node in the list
    public Node next;   // Reference to the previous node in the list
  
    // Constructor to initialize a new node with data
    public Node(int new_data) {
      data = new_data;
      prev = null;
      next = null;
    }
  }
  
  // Java Program to calculate the length of a Doubly Linked List
  public class FindLengthOfDDL {
  
    // Function to find and print the length of Doubly Linked List
    static void findLength(Node node) {
      int length = 0;
      while (node != null) {
        length++;
        node = node.next;
      }
      System.out.println("The Length of Doubly Linked List is: " + length);
    }
  
    public static void main(String[] args) {
      // Create a doubly linked list
      Node head = new Node(10);
      head.next = new Node(20);
      head.next.prev = head;
      head.next.next = new Node(30);
      head.next.next.prev = head.next;
      head.next.next.next = new Node(40);
      head.next.next.next.prev = head.next.next;
  
      // Find and print the length of a Doubly Linked List
      findLength(head);
    }
  }

Time Complexity: O(n), here n represent the total number of nodes in a doubly linked list.