public List <char> FindNodeMoves(int number, List <char> moves = null) { moves ??= new List <char>(); switch (number.CompareTo(this.Number)) { case -1: moves.Add('l'); LeftNode.FindNodeMoves(number, moves); break; case 1: moves.Add('r'); RightNode.FindNodeMoves(number, moves); break; } return(moves); }