/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> res;
    vector<int> tmp;
    int sum;
    void dfs(TreeNode* root, int cur){
        if(root->left == NULL && root->right == NULL){
            if(cur + root->val == sum){
                tmp.push_back(root->val);
                res.push_back(tmp);
                tmp.pop_back();
            }
            return ;
        }
        tmp.push_back(root->val);
        if(root->left)  dfs(root->left, cur + root->val);
        if(root->right) dfs(root->right, cur + root->val);
        tmp.pop_back();
    }
    vector<vector<int>> findPath(TreeNode* root, int _sum) {
        if(root == NULL)    return res;
        sum = _sum;
        dfs(root, 0);
        return res;
    }
};