No president who performs his duties faithfully and conscientiously can have any leisure.

学习数学的最好方法就是做数学。

作家的生活是一种不断被打断的生活。

The future belongs to the era of new energy.

竞争优势的真正来源是想象未来并创造未来的能力。

I could be bounded in a nutshell and count myself a king of infinite space.

一个问题如果在计算机上可以快速解决，那么它属于P类问题；如果一个解可以快速验证，那么它属于NP类问题。