leetcode

题目

https://leetcode-cn.com/problems/path-sum/

思路

深度优先遍历
从root遍历到叶子节点，看叶子节点的val是否等于剩余的targetSum

解法

  1. /**
  2.  * Definition for a binary tree node.
  3.  * function TreeNode(val, left, right) {
  4.  *     this.val = (val===undefined ? 0 : val)
  5.  *     this.left = (left===undefined ? null : left)
  6.  *     this.right = (right===undefined ? null : right)
  7.  * }
  8.  */
  9. /**
  10.  * @param {TreeNode} root
  11.  * @param {number} targetSum
  12.  * @return {boolean}
  13.  */
  14. var hasPathSum = function(root, targetSum) {
  15.     if (root === null) {
  16.         return false
  17.     }
  18.     if (!root.left && !root.right) {
  19.         return targetSum === root.val 
  20.     }
  21.     return hasPathSum(root.left, targetSum - root.val) || hasPathSum(root.right, targetSum - root.val)
  22. };