与IEnumerable.Intersect多个列表的交集（） [英] Intersection of multiple lists with IEnumerable.Intersect()

问题描述

我有我想要找的路口列表的列表是这样的：

I have a list of lists which I want to find the intersection for like this:

var list1 = new List<int>() { 1, 2, 3 };
var list2 = new List<int>() { 2, 3, 4 };
var list3 = new List<int>() { 3, 4, 5 };
var listOfLists = new List<List<int>>() { list1, list2, list3 };

// expected intersection is List<int>() { 3 };

有一些方法与IEnumerable.Intersect（）？

Is there some way to do this with IEnumerable.Intersect()?

编辑： 我应该更清楚这一点：我真的有一个列表的列表，我不知道有多少会出现，这三个名单上面只是一个例子，我有什么实际上是一个的IEnumerable＆LT ; IEnumerable的＆LT; SomeClass的＆GT;＆GT;

I should have been more clear on this: I really have a list of lists, I don't know how many there will be, the three lists above was just an example, what I have is actually an IEnumerable<IEnumerable<SomeClass>>

感谢所有伟大的答案。原来，有四个选项来解决这样的：列表+聚合（@Marcel戈塞尔林），列表+的foreach （@JaredPar，@Gabe Moothart），的HashSet +聚合（@jesperll）和的HashSet +的foreach （@Tony的小马）。我做了这些解决方案的一些性能测试（不同的列表的数量 若干要素每个列表和随机数最多的大小。

Thanks for all great answers. It turned out there were four options for solving this: List+aggregate (@Marcel Gosselin), List+foreach (@JaredPar, @Gabe Moothart), HashSet+aggregate (@jesperll) and HashSet+foreach (@Tony the Pony). I did some performance testing on these solutions (varying number of lists, number of elements in each list and random number max size.

事实证明，在大多数情况下的HashSet的性能比列表更好（因为HashSet的我猜的性质，除非有大名单，小的随机数的大小。） 我找不到的foreach方法和聚合方法之间的真正区别（在foreach方法执行的略的更好。）

It turns out that for most situations the HashSet performs better than the List (except with large lists and small random number size, because of the nature of HashSet I guess.) I couldn't find any real difference between the foreach method and the aggregate method (the foreach method performs slightly better.)

对我来说，总的方法真的再次呼吁所有（和我一起去，作为公认的答案），但我不会说这是最可读的解决方案..谢谢！

To me, the aggregate method is really appealing (and I'm going with that as the accepted answer) but I wouldn't say it's the most readable solution.. Thanks again all!

推荐答案

怎么样：

var intersection = listOfLists
    .Skip(1)
    .Aggregate(
        new HashSet<T>(listOfLists.First()),
        (h, e) => { h.IntersectWith(e); return h; }
    );

这样，它的优化利用和各地仍然在一条语句相同的HashSet。只要确保在listOfLists始终包含至少一个列表。

That way it's optimized by using the same HashSet throughout and still in a single statement. Just make sure that the listOfLists always contains at least one list.

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