使用LINQ查找数组中最常见的数字

List a = new List{ 1,1,2,2,3,4,5 }; 

使用LINQ最快的方法是什么？

我是LINQ的新手

Answer 1

这里的关键是使用Enumerable.GroupBy和聚合方法Enumerable.Count ：

 List list = new List() { 1,1,2,2,3,4,5 }; // group by value and count frequency var query = from i in list group i by i into g select new {g.Key, Count = g.Count()}; // compute the maximum frequency int whatsTheFrequencyKenneth = query.Max(g => g.Count); // find the values with that frequency IEnumerable modes = query .Where(g => g.Count == whatsTheFrequencyKenneth) .Select(g => g.Key); // dump to console foreach(var mode in modes) { Console.WriteLine(mode); } 

Answer 2

Jason的回答是正确的，但您可以在一个LINQ操作中执行此操作。

  List list = new List() { 1, 1, 2, 2, 3, 4, 5 }; // return most frequently occurring items var query = from i in list group i by i into g let maxFreq = (from i2 in list group i2 by i2 into g2 orderby g2.Count() descending select g2.Count()).First() let gCount = g.Count() where gCount == maxFreq select g.Key; // dump to console foreach (var mode in query) { Console.WriteLine(mode); } 

Answer 3

 public static Tres MostCommon(this IEnumerable source, Func transform) { return source.GroupBy(s => transform(s)).OrderByDescending(g => g.Count()).First().Key; } 

在具有整数类型的示例中，您可以将其称为：

 List a = new List{ 1,1,2,2,3,4,5 }; int mostCommon = a.MostCommon(x => x); 

Answer 4

 from num in a group num by num into numg let c = numg.Count() order by c descending select new { Number = numg.Key, Count = c } 

Answer 5

我认为最常见的号码也可以在这样的单一查询中实现 –

  var query = (from i in list group i by i into g orderby g.Count() descending select new { Key = g.Key, Count = g.Count() }).FirstOrDefault(); if (query == null) Console.WriteLine("query = NULL"); else Console.WriteLine("The number '{0}' occurs {1} times.", query.Key, query.Count); 

实际上不需要空检查但是当实际需要null时可能很有用（比如清空列表？）