Leetcode Path Sum

题意：判断是否存在从根结点到叶结点，路上结点之和为所给的值的路径。

思路：DFS。

class Solution {public:    bool hasPathSum(TreeNode* root, int sum) {        if(root == NULL) return false;                sum -= root->val;        bool leftmark = false;        bool rightmark = false;                if(root->left == NULL && root->right == NULL && sum == 0) return true;                        if(root->left) {            //if(sum == 0) leftmark =false;            leftmark = hasPathSum(root->left, sum);        }                if(root->right) {            //if(sum == 0) rightmark = false;            rightmark = hasPathSum(root->right, sum);        }                if(leftmark || rightmark) return true;        else return false;    }};