Count Total Nodes in Binary Tree in DSA Javascript - Build from Scratch

Count Total Nodes in Binary Tree

📖 Scenario: You are working with a simple binary tree data structure used in many applications like organizing data or searching quickly.Imagine a family tree where each person can have up to two children. We want to count how many people (nodes) are in this family tree.

🎯 Goal: Build a program that counts the total number of nodes in a binary tree using a simple recursive function.

📋 What You'll Learn

Create a binary tree using JavaScript objects with value, left, and right properties

Create a variable called root representing the root node of the tree

Create a function called countNodes that counts nodes recursively

Print the total number of nodes in the tree

💡 Why This Matters

🌍 Real World

Binary trees are used in many real-world applications like organizing data, searching quickly, and representing hierarchical information such as family trees or file systems.

💼 Career

Understanding binary trees and recursion is fundamental for software developers, especially those working with data structures, algorithms, and system design.

1

Create the Binary Tree

Create a variable called root that represents the root node of a binary tree with this exact structure:
{ value: 1, left: { value: 2, left: null, right: null }, right: { value: 3, left: null, right: null } }

DSA Javascript

// Create the root node of the binary tree
// Your code here

Hint

Use nested objects to represent the left and right children of the root node.

2

Create the Count Function

Create a function called countNodes that takes a parameter node and returns 0 if node is null.

DSA Javascript

const root = {
  value: 1,
  left: { value: 2, left: null, right: null },
  right: { value: 3, left: null, right: null }
};

// Create the countNodes function
// Your code here

Hint

Check if the node is null and return 0 to stop recursion.

3

Complete the Recursive Count Logic

Inside the countNodes function, return 1 + countNodes(node.left) + countNodes(node.right) to count the current node plus all nodes in the left and right subtrees.

DSA Javascript

const root = {
  value: 1,
  left: { value: 2, left: null, right: null },
  right: { value: 3, left: null, right: null }
};

function countNodes(node) {
  if (node === null) {
    return 0;
  }
  // Your code here
}

Hint

Count the current node as 1, then add counts from left and right children recursively.

4

Print the Total Number of Nodes

Use console.log to print the result of countNodes(root).

DSA Javascript

const root = {
  value: 1,
  left: { value: 2, left: null, right: null },
  right: { value: 3, left: null, right: null }
};

function countNodes(node) {
  if (node === null) {
    return 0;
  }
  return 1 + countNodes(node.left) + countNodes(node.right);
}

// Print the total number of nodes
// Your code here

Hint

The tree has 3 nodes: 1, 2, and 3.