计算列表中出现次数的方法 [英] A method to count occurrences in a list

问题描述

有一个简单的方法来计算一个列表中的所有元素出现在C＃中的同一个列表中的出现次数？

Is there a simple way to count the number of occurrences of all elements of a list into that same list in C#?

使用System：

using System;
using System.IO;
using System.Text.RegularExpressions;
using System.Collections.Generic;
using System.Linq;

string Occur;
List<string> Words = new List<string>();
List<string> Occurrences = new List<string>();

// ~170 elements added. . . 

for (int i = 0;i<Words.Count;i++){
    Words = Words.Distinct().ToList();
    for (int ii = 0;ii<Words.Count;ii++){Occur = new Regex(Words[ii]).Matches(Words[]).Count;}
         Occurrences.Add (Occur);
         Console.Write("{0} ({1}), ", Words[i], Occurrences[i]);
    }
}

推荐答案

关于这样的...

var l1 = new List<int>() { 1,2,3,4,5,2,2,2,4,4,4,1 };

var g = l1.GroupBy( i => i );

foreach( var grp in g )
{
  Console.WriteLine( "{0} {1}", grp.Key, grp.Count() );
}

编辑每个注释：我会尝试做这个正义。 ：）

Edit per comment: I will try and do this justice. :)

在我的例子中，它是一个 Func ，因为我的列表是ints。所以，我告诉GroupBy如何分组我的项目。 Func接受一个int并返回我的分组的键。在这种情况下，我会得到一个 IGrouping< int，int> （由int键入的int的分组）。例如，如果我将它改为（ i => i.ToString（）），我将通过字符串键入我的分组。你可以想象一个不太平凡的例子，而不是键入1，2，3...也许我做一个函数，返回一，两个，三 / p>



In my example, it's a Func<int, TKey> because my list is ints. So, I'm telling GroupBy how to group my items. The Func takes a int and returns the the key for my grouping. In this case, I will get an IGrouping<int,int> (a grouping of ints keyed by an int). If I changed it to (i => i.ToString() ) for example, I would be keying my grouping by a string. You can imagine a less trivial example than keying by "1", "2", "3" ... maybe I make a function that returns "one", "two", "three" to be my keys ...

private string SampleMethod( int i )
{
  // magically return "One" if i == 1, "Two" if i == 2, etc.
}

一个Func，它将接受一个int并返回一个字符串，就像...

So, that's a Func that would take an int and return a string, just like ...

i =>  // magically return "One" if i == 1, "Two" if i == 2, etc. 

但是，由于原始问题要求知道原始列表值及其计数，我只是使用整数来键入我的整数分组，使我的示例更简单。

But, since the original question called for knowing the original list value and it's count, I just used an integer to key my integer grouping to make my example simpler.

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