private bool CheckRows(char[][] board)
        {
            for (int i = 0; i < 9; i++)
            {
                var sudokuChecker = new SudokuChecker();
                for (int j = 0; j < 9; j++)
                {
                    if (!sudokuChecker.AddChar(board[i][j]))
                    {
                        return(false);
                    }
                }
            }

            return(true);
        }
        private bool CheckSquares(char[][] board)
        {
            for (int startIPoint = 0; startIPoint < 9; startIPoint += 3)
            {
                for (int startJPoint = 0; startJPoint < 9; startJPoint += 3)
                {
                    var sudokuChecker = new SudokuChecker();
                    for (int i = 0; i < 3; i++)
                    {
                        for (int j = 0; j < 3; j++)
                        {
                            if (!sudokuChecker.AddChar(board[startIPoint + i][startJPoint + j]))
                            {
                                return(false);
                            }
                        }
                    }
                }
            }

            return(true);
        }