/**
 * 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 {
private:
    vector<int> path;
    vector<vector<int>> ans;

public:
    vector<vector<int>> findPath(TreeNode* root, int sum) {
        dfs(root, sum);
        return ans;
    }

    void dfs(TreeNode* root, int sum) {
        if (!root) {
            return;
        }

        path.push_back(root->val);

        sum -= root->val;
        if (!root->left && !root->right && !sum) {
            ans.push_back(path);
        }

        dfs(root->left, sum);
        dfs(root->right, sum);

        path.pop_back();
    }
};