一种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

是否有一种简单的方法可以计算列表中所有元素在 C# 中出现在同一个列表中的次数?

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

像这样:

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

这样的事情怎么样...

How about something like this ...

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() );
}

按评论我会尽力做到这一点.:)

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

在我的例子中，它是一个 Func 因为我的列表是整数.所以，我告诉 GroupBy 如何对我的项目进行分组.Func 接受一个 int 并返回我的分组的键.在这种情况下，我将得到一个 IGrouping(由 int 键控的一组 int).例如，如果我将其更改为 (i => i.ToString() )，我将按字符串键控我的分组.你可以想象一个比键控1"、2"、3"更简单的例子......也许我制作了一个返回一"、二"、三"作为我的键的函数......

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.
}

所以，这是一个接受 int 并返回一个字符串的 Func，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，由于最初的问题要求知道原始列表值及其计数，因此我只是使用一个整数来键入我的整数分组以使我的示例更简单.

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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