0515-find-largest-value-in-each-tree-row.js

/**
 * 515. Find Largest Value in Each Tree Row
 * https://leetcode.com/problems/find-largest-value-in-each-tree-row/
 * Difficulty: Medium
 *
 * Given the root of a binary tree, return an array of the largest value in each row
 * of the tree (0-indexed).
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number[]}
 */
var largestValues = function(root) {
  if (!root) return [];
  const result = [];
  const queue = [root];

  while (queue.length) {
    const level = queue.length;
    let max = -Infinity;
    for (let i = 0; i < level; i++) {
      const node = queue.shift();
      max = Math.max(max, node.val);
      if (node.left) queue.push(node.left);
      if (node.right) queue.push(node.right);
    }
    result.push(max);
  }

  return result;
};