建立列表中项目计数的字典 [英] Building a dictionary of counts of items in a list

问题描述

我有一个列表，其中包含一堆可能会发生多次的字符串。我想拿这个清单，建立列表项目的字典作为关键字，并将其出现次数作为值。

示例：

 列表< string> stuff = new List< string>（）; 
 stuff.Add（花生酱）; 
 stuff.Add（Jam）; 
 stuff.Add（食物）; 
 stuff.Add（Snacks）; 
 stuff.Add（哲学）; 
 stuff.Add（花生酱）; 
 stuff.Add（Jam）; 
 stuff.Add（食物）; 
  

，结果将是一个字典，包含：

pre> 花生酱，2
果酱，2
食物，2
小吃，1
哲学，1


我有办法做到这一点，但似乎不像我'使用C＃3.0中的好东西

  public Dictionary< string，int> CountStuff（IList< string> stuffList）
 {
字典< string，int> stuffCount = new Dictionary< string，int>（）; 
 
 foreach（string stuff in stuffList）{
 //初始化或增加此项的计数
 if（stuffCount.ContainsKey（stuff））{
 stuffCount [东西] ++; 
} else {
 stuffCount.Add（stuff，1）; 
} 
} 
 
返回stuffCount; 
} 
  

解决方案

在C＃中执行此操作。

 列表< string> stuff = new List< string>（）; 
 ... 
 
 var groups =从s组中的s通过s选择
 new {Stuff = g.Key，Count = g.Count（）}; 
  

如果需要，您也可以直接调用扩展方法：

  var groups = stuff.GroupBy（s => s）.Select（
s => new {Stuff = s.Key，Count = s .Count（）}）; 
  

从这里，这是一个短跳到一个 Dictionary< string， int> ：

  var dictionary = groups.ToDictionary（g => g.Stuff，g = g.Count）; 
  

I have a List containing a bunch of strings that can occur more than once. I would like to take this list and build a dictionary of the list items as the key and the count of their occurrences as the value.

Example:

List<string> stuff = new List<string>();
stuff.Add( "Peanut Butter" );
stuff.Add( "Jam" );
stuff.Add( "Food" );
stuff.Add( "Snacks" );
stuff.Add( "Philosophy" );
stuff.Add( "Peanut Butter" );
stuff.Add( "Jam" );
stuff.Add( "Food" );

and the result would be a Dictionary containing:

"Peanut Butter", 2
"Jam", 2
"Food", 2
"Snacks", 1
"Philosophy", 1

I have a way to do this, but it doesn't seem like I'm utilizing the good stuff in C# 3.0

public Dictionary<string, int> CountStuff( IList<string> stuffList )
{
    Dictionary<string, int> stuffCount = new Dictionary<string, int>();

    foreach (string stuff in stuffList) {
        //initialize or increment the count for this item
        if (stuffCount.ContainsKey( stuff )) {
            stuffCount[stuff]++;
        } else {
            stuffCount.Add( stuff, 1 );
        }
    }

    return stuffCount;
}

解决方案

You can use the group clause in C# to do this.

List<string> stuff = new List<string>();
...

var groups = from s in stuff group s by s into g select 
    new { Stuff = g.Key, Count = g.Count() };

You can call the extension methods directly as well if you want:

var groups = stuff.GroupBy(s => s).Select(
    s => new { Stuff = s.Key, Count = s.Count() });

From here it's a short hop to place it into a Dictionary<string, int>:

var dictionary = groups.ToDictionary(g => g.Stuff, g => g.Count);

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