求个简单的C#算法

Question

一个指定长度的数组，求指定个数组成的所有子集并打印出来！比如说：string[8],找出由3个元素组成的所有子集！

Answer 1

参考： 字符串str,取n个字符的所有组合..
//这个不用我改成你需要的String[]吧，上次有个家伙给他参考，非让我改成int[]public String[] GetAllCombination(String str,Int32 n)  //n < str.Length 
        {
            Int32[] state = new Int32[str.Length];
            Char[] chars = str.ToCharArray();
            List<String> list = new List<String>();            for (Int32 i = 0; i < n; i++)
            {
                state[i] = 1;
            }
            for (Int32 i = n; i < state.Length; i++)
            {
                state[i] = 0;
            }            list.Add(str.Substring(0,n));
            while (true)
            {
                Boolean flag = true;
                Int32 index = 0;
                Int32 oneCount = 0;
                Int32 zeroCount = 0;
                StringBuilder sbuilder = new StringBuilder();                for(; index < state.Length - 1; index++)
                {
                    if (state[index] == 1 && state[index + 1] == 0)
                    {
                        Int32 temp = state[index];
                        state[index] = state[index + 1];
                        state[index + 1] = temp;
                        break;
                    }
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (state[i] == 0)
                        zeroCount++;
                    else
                        oneCount++;
                }                for (Int32 i = 0; i < index; i++)
                {
                    if (i < oneCount)
                        state[i] = 1;
                    else
                        state[i] = 0;
                }                for (Int32 i = 0; i < chars.Length; i++) 
                {
                    if (state[i] == 1)
                        sbuilder.Append(chars[i]);
                }                list.Add(sbuilder.ToString());                for (Int32 i = 0; i < chars.Length - n; i++)
                {
                    if (state[i] == 1)
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag)
                    break;
            }            return list.ToArray();
        }