112.path-sum.js

/*
 * @lc app=leetcode id=112 lang=javascript
 *
 * [112] Path Sum
 */
/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} sum
 * @return {boolean}
 */
var hasPathSum = function(root, sum) {
   // check 
  if (root === null) return false;
  //  if it's leaf:
  if (root.left === null && root.right === null) {
      return root.val === sum;
  }
  return (
    hasPathSum(root.left, sum - root.val) ||
    hasPathSum(root.right, sum - root.val)
  );
};