减去HashSets(并返回副本)? [英] Subtract HashSets (and return a copy)?

问题描述

我有一个HashSet，

I've got a HashSet,

var universe = new HashSet<int>();

还有一堆子集，

var sets = new List<HashSet<int>>(numSets);

我想减去一个块，我可以这样:

I want to subtract a chunk, which I can do like this:

var remaining = universe.ExceptWith(sets[0]);

但是ExceptWith是就地工作的.我不想修改universe.我应该先克隆它，还是有更好的方法?

But ExceptWith works in-place. I don't want to modify the universe. Should I clone it first, or is there a better way?

推荐答案

我想我应该克隆它 第一的?我该怎么办?

I guess I should clone it first? How do I do that?

var universe = new HashSet<int>();
var subset = new HashSet<int>();
...

// clone the universe
var remaining = new HashSet<int>(universe);
remaining.ExceptWith(subset);

不像Except扩展方法那样简单，但可能更快(您应该运行一些性能测试以确保成功)

Not as simple as with the Except extension method, but probably faster (you should run a few performance tests to make sure)

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