【练习】并查集经典习题

547. 省份数量 https://leetcode.cn/problems/number-of-provinces

1361. 验证二叉树 https://leetcode.cn/problems/validate-binary-tree-nodes

947. 移除最多的同行或同列石头 https://leetcode.cn/problems/most-stones-removed-with-same-row-or-column