【leetcode】Path Sum

Question：

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.

Anwser 1：    

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool hasPathSum(TreeNode *root, int sum) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(root == NULL){            return false;        }                int sub = sum - root->val;        if(sub == 0 && root->left == NULL && root->right == NULL){            return true;        }                bool left = hasPathSum(root->left, sub);        bool right = hasPathSum(root->right, sub);                return left || right;    }};