【LeetCode】路径总和 III

题目描述：

https://leetcode-cn.com/problems/path-sum-iii/

代码：

class Solution {
public:
    int pathSum(TreeNode* root, int sum) {
        int res = 0;
        if(!root)
            return 0;
        res+=Psum(root, sum);
        res+=pathSum(root->left, sum);
        res+=pathSum(root->right, sum);
        return res;
    }
    int Psum(TreeNode *root, int sum)
    {
        int res = 0;
        if(!root)
            return res;
        sum-=root->val;
        if(sum==0)
            res++;
        res+=Psum(root->left, sum);
        res+=Psum(root->right, sum);
        return res;
    }
};