https://www.luogu.com.cn/record/103820689 --> https://www.luogu.com.cn/blog/jinkel/solution-p3473

https://www.luogu.com.cn/record/102466969 --> https://www.luogu.com.cn/blog/88207/solution-p1587

https://www.luogu.com.cn/record/102564019 --> https://www.luogu.com.cn/blog/right-catblog/solution-p1781

（第三个略微有点牵强）