求改错：leetcode balanced binary tree

题目：Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

错误是：stack overflow. 在一个特大的testcase.

求帮忙看看哪里写的不对，然后怎么改。

谢谢大家~

把arraylist 换成set试一下 没必要留太多相同的值