摘要：
这篇随笔不是原创内容。 抄录 Stasys Jukna 所著 *Extremal Combinatorics* §1.6 The inclusion-exclusion principle。 The *principle of inclusion and exclusion* (sieve of E 阅读全文
「以解决问题为乐」
真的喜欢么？真的喜欢就去做吧。
Lost Boy Calling 。。。。
... Many of these issues are best dealt with at the algorithmic level, rather than by "tweaking" the code.
This is an obscurity that catches the unwary.
原来我什么都不懂。