public StringFeedback(FeedbackLevel level, StringFeedbackType sfType, HashSet <char> alphabet, CharSetSolver solver)
     : base(level, alphabet, 1, solver)
 {
     this.type   = FeedbackType.String;
     this.sfType = sfType;
 }
 public StringFeedback(FeedbackLevel level, StringFeedbackType sfType, HashSet<char> alphabet, CharSetSolver solver)
     : base(level, alphabet, 1, solver)
 {
     this.type = FeedbackType.String;
     this.sfType = sfType;
 }