使用枚举器求索引的全排列
caozhy使用枚举器求索引的全排列是个好办法，学习了一下，重新写了一个函数。

/// <summary>
/// 使用枚举器生成[n, count)索引全排列 。
/// </summary>
/// <param name="count">数目，索引在[0, count - 1]间 。</param>
/// <returns>索引全排列 。</returns>
/// <exception cref="ArgumentOutOfRangeException">如果count非法，抛出ArgumentOutOfRangeException 。</exception>
public static IEnumerable<IList<int>> PermutationIndice(int count)
{
if (count < 0)
{
throw new ArgumentOutOfRangeException("count");
}

IEnumerable<int> allIndice = Enumerable.Range(0, count);
IEnumerable<IList<int>> permutation = null;
for (int i = 0; i < count; i++)
{ // 每次迭代，求i个索引的排列全集
if (i == 0)
{
permutation = Enumerable.Select<int, IList<int>>(allIndice, x => new int[] { x });
//permutation = allIndice.Select<IList<int>>(x => new int[] { x });
}
else
{
permutation = Enumerable.SelectMany<IList<int>, IList<int>>(permutation,
l => Enumerable.Select<int, IList<int>>(allIndice.Except(l), x => new List<int>(l).Concat(new int[] { x }).ToList()));
//l => allIndice.Except(l).SelectMany<IList<int>>(x => new List<int>(new List<int>(l).Concat(new int[] { x}).ToList())));
}
}

return permutation;
}

[解决办法]

C# code

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace ConsoleApplication1{    class Program    {        static void Main(string[] args)        {            var result = Arrange(4);            foreach (var item in result)            {                Console.WriteLine(string.Join(",", item.Select(x => x.ToString()).ToArray()));            }        }        static IEnumerable<IEnumerable<int>> Arrange(int n)        {            IEnumerable<IEnumerable<int>> result = Enumerable.Range(0, n).Select(x => new List<int>() { x });            while (result.First().Count() < n)            {                result = result.SelectMany(x => Enumerable.Range(0, n).Except(x).Select(y => x.Concat(new List<int>() { y })));            }            return result;        }    }}