二叉树中的回溯

上来就回溯，别问为什么,综合评分也还凑合，贴一下吧

运行时间：16ms
超过80.33% 用Java提交的代码
占用内存：9736KB
超过73.69%用Java提交的代码

public ArrayList<ArrayList<Integer>> FindPath(TreeNode root, int target) {
        ArrayList<ArrayList<Integer>> res = new ArrayList<>();
        ArrayList<Integer> path = new ArrayList<>();
        if (root == null) return res;
        findPathBackTrace(root, target, res, path);
        return res;
    }
    public void findPathBackTrace(TreeNode node, int remains, ArrayList<ArrayList<Integer>> res, ArrayList<Integer> path) {
        if (node == null) return;
        if (node.left == null && node.right == null) {
            if (remains == node.val) {
                path.add(node.val);
                res.add(new ArrayList<>(path));
                path.remove(path.size() - 1);
            }
            return;
        } else if (remains < node.val) {
            return;
        }
        path.add(node.val);
        findPathBackTrace(node.left, remains - node.val, res, path);
        findPathBackTrace(node.right, remains - node.val, res, path);
        path.remove(path.size() - 1);
    }