0104-maximum-depth-of-binary-tree.js

/**
 * 104. Maximum Depth of Binary Tree
 * https://leetcode.com/problems/maximum-depth-of-binary-tree/
 * Difficulty: Easy
 *
 * Given the root of a binary tree, return its maximum depth.
 *
 * A binary tree's maximum depth is the number of nodes along the longest
 * path from the root node down to the farthest leaf node.
 */

/**
 * 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 maxDepth = function(root) {
  if (!root) {
    return 0;
  }
  const [left, right] = [root.left, root.right].map(maxDepth);
  return 1 + Math.max(left, right);
};