[Leetcode] 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.

 

水！

 

 1 /**

 2  * Definition for binary tree

 3  * struct TreeNode {

 4  *     int val;

 5  *     TreeNode *left;

 6  *     TreeNode *right;

 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 8  * };

 9  */

10 class Solution {

11 public:

12     bool hasPathSum(TreeNode *root, int sum) {

13         if (root == NULL) {

14             return false;

15         }

16         if (root->left == NULL && root->right == NULL) {

17             return root->val == sum;

18         }

19         bool flag1 = hasPathSum(root->left, sum - root->val);

20         bool flag2 = hasPathSum(root->right, sum - root->val);

21         return flag1 || flag2;

22     }

23 };