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 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @param target int整型 
     * @return int整型ArrayList<ArrayList<>>
     */
    ArrayList<ArrayList<Integer>> path = new ArrayList<ArrayList<Integer>>();
    public ArrayList<ArrayList<Integer>> FindPath (TreeNode root, int target) {
        // write code here
    ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
    ArrayList<Integer> sub_path = new ArrayList<Integer>();
    help(root, target, 0, sub_path, result);
    return result;
    }

  void help(TreeNode root, int target, int sum, ArrayList<Integer> sub_path, ArrayList<ArrayList<Integer>> result) {
    if (root == null) return;
    sum += root.val;
    sub_path.add(root.val);
    if (sum == target && root.left == null && root.right == null) {
      result.add(new ArrayList<Integer>(sub_path));
    }
    help(root.left, target, sum, new ArrayList<Integer>(sub_path), result);
    help(root.right, target, sum, new ArrayList<Integer>(sub_path), result);
  }
}