稍微做的有点久,学到了两点:用负数(或为用到的int范围)来代表布尔值剪枝操作。如该题的搜索其实还是遵循的后续遍历,所以实际上时间复杂度是O(N) 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 { /*...