$O(N^2)$ 算法怎么可能过得了

https://www.luogu.com.cn/blog/lc-2018-Canton/solution-p5094

https://www.luogu.com.cn/blog/hf45LLR/solution-p5094

https://www.luogu.com.cn/blog/zhaoshuaiqi/solution-p5094