public RuleBasedSolver(string puzzle)
{
board = new Board();
board.SetBoard(puzzle);
}
/// <summary>
/// Constructor which initialises the puzzle with the given grid.
/// </summary>
/// <param name="grid">A 9 by 9 int array which describes a puzzle grid. It has to be 9 by 9.</param>
public RuleBasedSolver(int[,] grid)
{
board = new Board();
board.SetBoard(grid);
}