/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    private List<List<Integer>> res = new ArrayList<>();
    public List<List<Integer>> findPath(TreeNode root, int sum) {
        dfs(root, sum, new ArrayList<>());
        return res;
    }

    private void dfs(TreeNode node , int target , List<Integer> path) {
        if (node == null) {
            return;
        }
        path.add(node.val);
        target -= node.val;
        if (target == 0 && node.left == null && node.right == null) {
            res.add(new ArrayList<>(path));
        } else {
            dfs(node.left, target, path);
            dfs(node.right, target, path);
        }
        path.remove(path.size() - 1);
    }
}