输入一个字符串，输出该字符串中元素的所有组合子串

例如输入{abc}，则输出有{}，{a}，{b}，{c}，{ab}，{ac}，{bc}，{abc}

C# 递归 codes：

static void Main(string[] args)

{

string[] outStr=OutputString("ABC");

foreach(string str in outStr)

{

Console.WriteLine(str);

}

Console.ReadKey();

}

static string[] OutputString(string str)

{

if (str == string.Empty)

{

return new string[] { string.Empty };

}

string[] result = new string[1 << str.Length];

for (int i = 0; i < 1 << str.Length - 1; i++)

{

result[i] = OutputString(str.Remove(0, 1))[i];

}

for (int i = 1 << str.Length - 1; i < 1 << str.Length; i++)

{

result[i] = string.Format("{0}{1}", str[0], OutputString(str.Remove(0, 1))[i - (1 << str.Length - 1)]);

}

return result;

}

output result:

C

B

BC

A

AC

AB

ABC