Because if you did what I suggested with the list, the time to look up the key would be linear in the length of the list. You'd have to look at each element until you found the key.

字典是用一种很神奇的，叫做散列法的算法,来实现的，后面我们将,会学到一点关于。

麻省理工公开课 - 计算机科学及编程导论课程节选

It's not true, by the way, of all programming languages. In fact, Professor Guttag already talked about that, in some languages lists take a time linear with the length to get to it.

顺便说一句这在大部分，编程语言中做不到，实际上Guttag教授已经说过这一点了，在一些语言中取得数组,要花费时间是线性长度的。

麻省理工公开课 - 计算机科学及编程导论课程节选