[leetCode刷题笔记]113. Path Sum II

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public List<List<Integer>> pathSum(TreeNode root, int sum) {        List<List<Integer>> res = new ArrayList<List<Integer>>();        List<Integer> path = new ArrayList<Integer>();        helper(root, sum, path, res);        return res;    }        private void helper (TreeNode root, int sum, List<Integer> path, List<List<Integer>> res) {        if (root == null) {                        return;        }        path.add(root.val);        if (root.left == null && root.right == null) {            if (sum == root.val) {                res.add(new ArrayList<Integer>(path));            }            path.remove(path.size() - 1);            return;        }        helper(root.left, sum - root.val, path, res);        helper(root.right, sum - root.val, path, res);        path.remove(path.size() - 1);        return;    }}