So the problem here, roughly, is given, a number of cities, and say the cost of traveling from city to city by airplane, what's the least cost round trip that you can find?

基本上就是一个这样的问题,你被告知了一些城市,以及在城市之间坐飞机旅行的花费,那一条是你们能找到最短往返路径？

麻省理工公开课 - 计算机科学及编程导论课程节选

So that you take every sodium and you count all of its nearest neighbors, next nearest neighbors, next next nearest neighbors, not only on a line but in the plane and above and below in all three dimensions and go through that calculation, it is even more negative.

你考虑到每一个钠原子,你要考虑到它最近的原子，第二近的原子，第三近的原子，不是在一条线而是在一个面上,以及面上与面下的三维空间,再完成计算，这将会更负。

麻省理工公开课 - 固态化学导论课程节选