学历史,学历史。历史里藏着一切的智慧。

Out, out, brief candle! Life's but a walking shadow, a poor player That struts and frets his hour upon the stage And then is heard no more. It is a tale Told by an idiot, full of sound and fury, Signifying nothing, 

"We are all in the gutter, but some of us are looking at the stars."

NP中的每个问题都可以归约为可满足性问题，这是计算复杂性理论的基石。