题解 | #二叉树中和为某一值的路径(二)#

import java.util.*;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {

    private ArrayList<ArrayList<Integer>> res = new ArrayList<>();

    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root, int expectNumber) {
        if (root == null) {
            return res;
        }
        dfs(root, expectNumber, new ArrayList<>());
        return res;
    }

    private void dfs(TreeNode root, int target, List<Integer> list) {
        if (root == null) {
            return;
        }
        target -= root.val;
        list.add(root.val);
        if (root.left == null && root.right == null && target == 0) {
            res.add(new ArrayList<>(list));
        }

        dfs(root.left, target, list);
        dfs(root.right, target, list);
        list.remove(list.size() - 1);
    }
}