https://www.luogu.com.cn/article/x8jm95s1

https://www.luogu.com.cn/article/1d6ti0i7

https://www.luogu.com.cn/article/9hd7ejzi

https://www.luogu.com.cn/article/m9x697eo

还有另外一道类似题目的：

https://www.luogu.com.cn/article/i00um1wa

原因：复杂度有误，容易误导小朋友