我什么时候应该使用 HashSet<T>类型? [英] When should I use the HashSet<T> type?

问题描述

我正在探索 HashSet 类型，但我不明白它在集合中的位置.

I am exploring the HashSet<T> type, but I don't understand where it stands in collections.

可以用它来代替List吗?我想象 HashSet 的性能会更好，但我看不到对其元素的单独访问.

Can one use it to replace a List<T>? I imagine the performance of a HashSet<T> to be better, but I couldn't see individual access to its elements.

仅用于枚举吗?

推荐答案

HashSet 的重要之处就在于它的名字:它是一个 set.对于单个集合，您唯一可以做的就是确定它的成员是什么，并检查一个项目是否是成员.

The important thing about HashSet<T> is right there in the name: it's a set. The only things you can do with a single set is to establish what its members are, and to check whether an item is a member.

询问是否可以检索单个元素(例如 set[45])是对集合概念的误解.没有集合的第 45 个元素这样的东西.集合中的项目没有顺序.集合 {1, 2, 3} 和 {2, 3, 1} 在各方面都是相同的，因为它们具有相同的成员资格，而成员资格才是最重要的.

Asking if you can retrieve a single element (e.g. set[45]) is misunderstanding the concept of the set. There's no such thing as the 45th element of a set. Items in a set have no ordering. The sets {1, 2, 3} and {2, 3, 1} are identical in every respect because they have the same membership, and membership is all that matters.

迭代 HashSet 有点危险，因为这样做会对集合中的项目强加一个顺序.该顺序并不是该集合的真正属性.你不应该依赖它.如果集合中项目的排序对您很重要，则该集合不是集合.

It's somewhat dangerous to iterate over a HashSet<T> because doing so imposes an order on the items in the set. That order is not really a property of the set. You should not rely on it. If ordering of the items in a collection is important to you, that collection isn't a set.

集合真的很有限，并且有独特的成员.另一方面，它们真的很快.

Sets are really limited and with unique members. On the other hand, they're really fast.

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