C#写的一段求子集的程序，希望高手帮忙改进

[johnshen0211]

如题，程序如下:
using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Text.RegularExpressions;

namespace TestSubSet
{
class Program
{
static void Main(string[] args)
{
Regex r = new Regex(",");

ArrayList al = new ArrayList();
//al.Add("A,B,C,D");
al.Add("A,B,C");
Console.WriteLine("A,B,C的子集是:");
ArrayList alsubset = new ArrayList();

for (int i = 0; i < al.Count; i++)
{

string[] s = r.Split(al[i].ToString());

string str = "";
for (int j = 0; j < s.Length; j++)
str = str + s[j].ToString();

//调用求子集函数
alsubset = subSet(str);

alsubset.Sort();

//将子集进行输出
for (int j = 0; j < alsubset.Count; j++)
Console.WriteLine(alsubset[j].ToString());

}



Console.ReadLine();
}

static ArrayList subSet(string str)
{
ArrayList al = new ArrayList();

for (int i = 0; i < str.Length; ++i)
{
getSub(str, i, al);
}

return al;
}

static void getSub(string str, int i, ArrayList al)
{

str = str.Remove(i, 1);

if (!al.Contains(str) && str != "")
{
al.Add(formatStr(str));
}
else
{
return;
}

for (int j = 0; j < str.Length; ++j)
{
getSub(str, j, al);
}

}

static string formatStr(string str)
{
string fstr = str.Substring(0,1);
for (int i = 1; i < str.Length; i++)
fstr = fstr + "," + str.Substring(i, 1);
return fstr;
}
}
}
程序运行结果如下：
Console.WriteLine("A,B,C的子集是:");
A
A,B
A,C
B
B,C
C

谢谢！

[simen_frankly]

你不是都写了吗？
我说一下我的思路
首先将A,B,C以逗号split，然后放入数组中，str[1],str[2],str[3]取数全排列就是了，不知道对你是否有帮助？？

[xuezaiyue]

直接用位操作好了，计算ABCDEFGHIJKLMN只需一秒钟：

        static void Main(string[] args)
        {
            string set = "ABCDEFGHIJKLMN";
            string[] subsets = GetSubSet(set);
            foreach (string s in subsets)
            {
                Console.WriteLine(s);
            }
        }

        static string[] GetSubSet(string set)
        {
            List<string> subsets = new List<string>();
            for (int i = 0; i < (1 << set.Length); i++)
            {
                string s = "";
                for (int j = 0; j < set.Length; j++)
                {
                    if ((i & (1 << j)) != 0)
                    {
                        s += set[j];
                    }
                }
                subsets.Add(s);
            }
            return subsets.ToArray();
        }

输出:
A
B
AB
C
AC
BC
ABC
D
AD
BD
ABD
CD
ACD
BCD
ABCD
E
AE
...
ABCDEFGHIJKLMN