private bool FindSolution(Board board, int index)
{
int row = index/SIZE, column = index%SIZE;
if (index == SIZE*SIZE) return true;
if (board.IsFilled(row, column)) return FindSolution(board, index+1);
foreach(int value in board.GetOptionsForCell(row, column))
{
board.SetCellValue(row, column, value);
if (FindSolution(board, index+1)) return true;
}
board.ClearCell(row, column);
return false;
}
