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.

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */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) {return dfs(root,sum,0);    }private:bool dfs(TreeNode *root,int sum,int n){if(root == NULL) return false;n += root->val;if(root->left == NULL && root->right == NULL) return n == sum;return dfs(root->left,sum,n) || dfs(root->right,sum,n);}};