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Breadth-First Search for Advanced Binary Tree Problems in JavaScript

Explore how Breadth-First Search can be effectively used to calculate the maximum sum of nodes at any level in a binary tree, implemented in JavaScript.

Applying Breadth-First Search to Find Maximum Level Sum in Binary Trees

Breadth-First Search (BFS) is an essential tree traversal technique, especially effective for binary trees when processing nodes level by level. This method is particularly useful for calculating the maximum sum of node values at each level of the tree.

Why Breadth-First Search in Binary Trees?

  • Systematic Level Traversal: Breadth-First Search ensures a thorough exploration of each tree level, making it suitable for level-specific calculations.
  • Optimal for Wide Trees: In broad or wide binary trees, Breadth-First Search can be more efficient than depth-first strategies.
  • Queue-Based Implementation: BFS can be elegantly implemented using a queue, allowing for a straightforward and efficient traversal of the binary tree.

Understanding the Basics:

Breadth-First Search operates using a queue to manage the nodes at each level, ensuring all nodes on one level are processed before moving to the next.

Example: Calculating Maximum Level Sum

Problem Statement:

Create a function to determine the maximum sum of node values at any level in a binary tree.

class TreeNode {
  constructor(value) {
    this.value = value;
    this.left = null;
    this.right = null;

function maxLevelSum(root) {
  if (!root) return 0;
  let queue = [root];
  let maxSum = root.value;

  while (queue.length) {
    let levelSize = queue.length;
    let levelSum = 0;

    for (let i = 0; i < levelSize; i++) {
      let currentNode = queue.shift();
      levelSum += currentNode.value;

      if (currentNode.left) queue.push(currentNode.left);
      if (currentNode.right) queue.push(currentNode.right);

    maxSum = Math.max(maxSum, levelSum);

  return maxSum;

How the Code Works:

  • TreeNode Class: A class to construct nodes for the binary tree.
  • Breadth-First Search Function: Utilizes a queue to iterate through each tree level.
  • Summing Node Values: Accumulates the sum of values at each level.
  • Identifying Maximum Sum: Continuously updates the maximum sum encountered across levels.

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