Coderbyte - question marks

questions.cs

  private static readonly Regex rx = new Regex(@"(\d)(\D+)?");

  public static string QuestionsMarks(string str) {
    var input = rx.Matches(str).Select(m => Tuple.Create(Int32.Parse(m.Groups[1].Value), m.Groups[2].Value)).ToList();
    return input
      .Zip(input.Skip(1), Tuple.Create)
      .Where(t => t.Item1.Item1 + t.Item2.Item1 == 10)
      .DefaultIfEmpty(Tuple.Create(Tuple.Create(0, ""), Tuple.Create(0, "")))
      .All(t => t.Item1.Item2.Count(c => c == '?') == 3)
      .ToString()
      .ToLower();
  }