113. Path Sum II

Problem:

思路：

Solution (C++):

public:
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        vector<vector<int>> res;
        vector<int> path;
        pathSum(res, sum, root, path);
        
        return res;
    }
private:
    void pathSum(vector<vector<int>> &res, int sum, TreeNode *root, vector<int> &path) {
        if (!root)  return;
        path.push_back(root->val);
        if (sum == root->val && !(root->left) && !(root->right))
            res.push_back(path);
        pathSum(res, sum - root->val, root->left, path);
        pathSum(res, sum - root->val, root->right, path);
        path.pop_back();
    }

性能：

Runtime: 20 ms  Memory Usage: 19.9 MB