从长度为n c#的列表中获取所有可能的字符串对[重复]

Question

我有一个字符串列表

List<String> points = new List<String>();

假设点包含 [A,B,C,D,E]。我想要列表中所有可能的配对。我的预期输出是`

[A,B],
[A,C],
[A,D],
[A,E],
[B,A],
[B,C],
[B,D],
[B,E],
[C,A],
[C,B],
[C,D],
[C,E],
[D,A],
[D,B],
[D,C],
[D,E],
[E,A],
[E,B],
[E,C],
[E,D]

我需要获得所有 20 种组合。你能帮我在c#中解决这个问题吗？

Answer 1

我决定使用 LINQ（因为我可以而且很有趣）：

public static void Main (string[] args) {
        List<String> points = new List<String> {"A","B", "C", "D", "E"};

        var perm = (from i in points.Select((Value, Index) => new { Value, Index })
                   from j in points.Select((Value, Index) => new { Value, Index })
                   where i.Index != j.Index
                   select (i.Value, j.Value)).ToList();

        foreach(var item in perm)
        {
            Console.WriteLine($"[{item.Item1},{item.Item2}]");
        }    
    }

---

输出：

[A,B]
[A,C]
[A,D]
[A,E]
[B,A]
[B,C]
[B,D]
[B,E]
[C,A]
[C,B]
[C,D]
[C,E]
[D,A]
[D,B]
[D,C]
[D,E]
[E,A]
[E,B]
[E,C]
[E,D]

Answer 2

我首先想到的是使用 ValueTuples 和简单的循环，如下所示：

void Main()
{
   List<string> strings = new List<string> () {"A", "B", "C", "D", "E"};

   foreach (var item in OutputCombinations(strings))
   {
      Console.WriteLine($"[{item.Item1}{item.Item2}]");
   }
}

以及组合方法：

public static List<ValueTuple<string, string>> OutputCombinations(List<string> list)
{
   List<ValueTuple<string, string>> pairs = new List<ValueTuple<string, string>>();

   ValueTuple<string, string> currentPair = new ValueTuple<string, string>();
   for (int i = 0; i < list.Count; i++)
   {
       currentPair.Item1 = list[i];

       for (int j = 0; j < list.Count; j++)
       {
           if (i != j)
           {
            currentPair.Item2 = list[j];

            pairs.Add(currentPair);
           }
       }
   }

return pairs;
}

输出：

[AB]
[AC]
[AD]  
[AE]
[BA]
[BC]
[BD]
[BE]
[CA]
[CB]
[CD]
[CE]
[DA]
[DB]
[DC]
[DE]
[EA]
[EB]
[EC]
[ED]