[LeetCode][JavaScript]Path Sum

Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / 
            4   8
           /   / 
          11  13  4
         /        
        7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

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

判断是否有一条从根到叶子的路径的和为sum。

如果不是叶子节点，递归进去，如果是叶子节点，计算路径是不是等于sum。

两道类似的题：

Binary Tree Paths : http://www.cnblogs.com/Liok3187/p/4735368.html

Path Sum II : http://www.cnblogs.com/Liok3187/p/4869538.html

 1 /**
 2  * Definition for a binary tree node.
 3  * function TreeNode(val) {
 4  *     this.val = val;
 5  *     this.left = this.right = null;
 6  * }
 7  */
 8 /**
 9  * @param {TreeNode} root
10  * @param {number} sum
11  * @return {boolean}
12  */
13 var hasPathSum = function(root, sum) {
14     if(root && root.val !== undefined){
15         return hasSum(root, 0);
16     }
17     return false;
18 
19     function hasSum(node, value){
20         var isLeaf = true, tmp;
21         if(node.left){
22             isLeaf = false;
23             tmp = hasSum(node.left, value + node.val);
24             if(tmp === true){
25                 return true;
26             }
27         }
28         if(node.right){
29             isLeaf = false;
30             tmp = hasSum(node.right, value + node.val);
31             if(tmp === true){
32                 return true;
33             }
34         }
35         if(isLeaf){
36             tmp = value + node.val;
37             if(tmp === sum){
38                 return true;
39             }
40         }
41         return false;
42     }
43 };

原文地址：https://www.cnblogs.com/Liok3187/p/4869521.html