给定一个集合，求出其所有子集合

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
class Program
/**//// <summary>
/// 函数：给定一个集合，求出其所有子集合
/// </summary>
private static List<string> printList(string[] arr, int num)
if (num < 0)
List<string> reto = new List<string>();
reto.Add("");
return reto;
}
else
List<string> ret = printList(arr, num - 1);
List<string> addRet = new List<string>();
ret.ForEach(delegate(string x) ret.AddRange(addRet);
return ret;
}
}
static void Main(string[] args)
//演示
string[] arr = List<string> ret = printList(arr, 2);
ret.ForEach(delegate(string x) Console.Read();
}
}
}