DouKaku?

using System;
using System.Text;
class Program
{
  static void Main(string[] args)
  {
    Console.WriteLine(RemoveBlockComment("AAA"));
    Console.WriteLine(RemoveBlockComment("AAA/*/BBB"));
    Console.WriteLine(RemoveBlockComment("AAA/*BBB"));
    Console.WriteLine(RemoveBlockComment("AAA/*BBB*/CCC"));
    Console.WriteLine(RemoveBlockComment("AAA/*BBB/*CCC*/DDD*/EEE"));
    Console.WriteLine(RemoveBlockComment("AAA/a//*BB*B**/CCC"));
  }

  static string RemoveBlockComment(string s)
  {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.Length; ++i)
    {
      if (i < s.Length - 1 && s[i] == '/' && s[i + 1] == '*')
      {
        i += 3;
        while (i < s.Length && (s[i - 1] != '*' || s[i] != '/')) ++i;
      }
      else sb.Append(s[i]);
    }
    return sb.ToString();
  }
}