124.binary-tree-maximum-path-sum.js

/*
 * @lc app=leetcode id=124 lang=javascript
 *
 * [124] Binary Tree Maximum Path Sum
 */
/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var maxPathSum = function (root) {
  let res = -Infinity
  function helper(node) {
    if (!node) return 0
    const left = Math.max(helper(node.left), 0)
    const right = Math.max(helper(node.right), 0)
    res = Math.max(res, left + right + node.val)
    return Math.max(left, right) + node.val
  }
  helper(root)
  return res
};