leetcode---path-sum---树

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 andsum = 22,
5
/ \
4 8
/ / \
11 13 4
/ \ \
7 2 1
return true, as there exist a root-to-leaf path5->4->11->2which sum is 22.

/** * 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 dfs(int tmp, TreeNode *root, int sum)    {        if(!root)            return false;        if(!root->left && !root->right)            return tmp + root->val == sum;        if(dfs(tmp+root->val, root->left, sum))            return true;        if(dfs(tmp+root->val, root->right, sum))            return true;        return false;    }    bool hasPathSum(TreeNode *root, int sum)     {        if(!root)            return false;        return dfs(0, root, sum);    }};