我怎样才能得到输出字符串数组所有的可能性与组合？

Question

我需要任何字符串列表输出所有可能性。像那样。 这是让我720不同的字符串。

List<String> items = new List<String>(); 
     items.AddRange(new String[] { "a", "b", "c", "d", "e", "f" }); 

输出;

1-）ABCDEF

2-）abcdfe

3-）ABCEDF

4-）abcefd

5-）abcfde

6-）abcfed

7-）abdcef

8-）abdcfe

9-）abdecf

10-）abdefc

11-）...........

12-）.. .........

13-）bacdef

720 - ）..........

Answer 1

在这里你去：

using System; 
using System.Collections.Generic; 
using System.Linq; 

namespace ConsoleApplication2 
{ 
    class Program 
    { 
     static void Main() 
     { 
      List<String> items = new List<String>(); 
      items.AddRange(new String[] { "a", "b", "c", "d", "e", "f" }); 

      int i = 0; 

      foreach (var permutation in Permute(items)) 
       Console.WriteLine(++i + ": " + string.Join(" ", permutation)); 
     } 

     public static IEnumerable<IEnumerable<T>> Permute<T>(IEnumerable<T> seq) 
     { 
      return 
       from item in seq.Select((value, index) => new {value, index}) 
       from remainder in seq.Count() == 1 ? new[]{new T[0]} : Permute(allExcept(seq, item.index)) 
       select new[]{item.value}.Concat(remainder); 
     } 

     static IEnumerable<T> allExcept<T>(IEnumerable<T> seq, int indexToSkip) 
     { 
      return 
       from item in seq.Select((value, index) => new {value, index}) 
       where item.index != indexToSkip 
       select item.value; 
     } 
    } 
} 

如果您在输入重复的字符串，并要消除重复排列在输出中，然后使用DistinctBy()（originally written by Jon Skeet），像这样：

var uniquePerms = Permute(items).DistinctBy(p => string.Join(" ", p)); 

其中DistinctBy()是IEnumerable<T>的扩展方法：

public static class EnumerableExt 
{ 
    public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) 
    { 
     return source.DistinctBy(keySelector, null); 
    } 

    public static IEnumerable<TSource> DistinctBy<TSource, TKey>(
     this IEnumerable<TSource> source, 
     Func<TSource, TKey> keySelector, 
     IEqualityComparer<TKey> comparer) 
    { 
     return distinctByImpl(source, keySelector, comparer); 
    } 

    static IEnumerable<TSource> distinctByImpl<TSource, TKey>(
     IEnumerable<TSource> source, 
     Func<TSource, TKey> keySelector, 
     IEqualityComparer<TKey> comparer) 
    { 
     var knownKeys = new HashSet<TKey>(comparer); 
     return source.Where(element => knownKeys.Add(keySelector(element))); 
    } 
}