在C#的列表中获取通用元素 [英] get common elements in lists in C#

问题描述

我有两个排序列表，如下所示:

I have two sorted lists as below:

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

我希望输出为:{1, 1, 2}

如何在C#中执行此操作? 有没有使用Linq的方法?

How to do this in C#? Is there a way using Linq?

推荐答案

多余的1表示您不能使用Intersect，因为它会返回一个集合.

The extra 1 means you can't use Intersect because it returns a set.

以下代码可以满足您的需求:

Here's some code that does what you need:

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

var grouped1 =
    from n in list1
    group n by n
    into g
    select new {g.Key, Count = g.Count()};

var grouped2 =
    from n in list2
    group n by n
    into g
    select new {g.Key, Count = g.Count()};

var joined =
    from b in grouped2
    join a in grouped1 on b.Key equals a.Key
    select new {b.Key, Count = Math.Min(b.Count, a.Count)};

var result = joined.SelectMany(a => Enumerable.Repeat(a.Key, a.Count));

CollectionAssert.AreEquivalent(new[] {1, 1, 2}, result);

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