public SolverResult TryToSolveOneCell(Grid grid, PencilMarks pencilMarks)
{
foreach (var column in grid.Columns())
{
var digitsToFillIn = grid.AllowedDigits
.Where(digit => column.DoesNotContain(digit));
foreach (var digit in digitsToFillIn)
{
var possibleRows = column.EmptyRows()
.Where(rowNumber => pencilMarks.HasMark(column.ColumnNumber, rowNumber, digit));
switch (possibleRows.Count())
{
case 0:
throw new Exception("Grid can't be solved");
case 1:
var newCell = new Cell(column.ColumnNumber, possibleRows.First());
var updatedGrid = grid.FillInSquare(column.ColumnNumber, possibleRows.First(), digit);
return(SolverResult.Success(updatedGrid, newCell, $"This is the only cell in this column where {digit} can go."));
default:
break;
}
}
}
return(SolverResult.Failed(grid));
}
internal bool DoesNotContain(PencilMarks pencilMarks, char digit)
{
for (int row = 0; row < 9; row++)
{
if (pencilMarks.HasMark(ColumnNumber, row, digit))
{
return(false);
}
}
return(true);
}
internal bool DoesNotContain(PencilMarks pencilMarks, char digit)
{
for (int columnNumber = 0; columnNumber < 9; columnNumber++)
{
if (pencilMarks.HasMark(columnNumber, RowNumber, digit))
{
return(false);
}
}
return(true);
}
internal bool DoesNotContain(PencilMarks pencilMarks, char digit)
{
for (int column = 0; column < 3; column++)
{
for (int row = 0; row < 3; row++)
{
if (pencilMarks.HasMark(column + Left, row + Top, digit))
{
return(false);
}
}
}
return(true);
}
public List <string> Evaluate(Grid grid, PencilMarks pencilMarks)
{
var result = new List <string>();
foreach (var box in grid.Boxes())
{
foreach (var digit in grid.AllowedDigits)
{
if (box.DoesNotContain(digit))
{
var columns = new int[3];
var rows = new int[3];
for (int x = 0; x < 3; x++)
{
for (int y = 0; y < 3; y++)
{
if (pencilMarks.HasMark(box.Left + x, box.Top + y, digit))
{
columns[x]++;
rows[y]++;
}
}
}
if (columns[0] > 0 && columns[1] == 0 && columns[2] == 0)
{
RemoveFromVerticallyAdjacentBoxes(box, 0, pencilMarks, digit, result);
}
if (columns[0] == 0 && columns[1] > 0 && columns[2] == 0)
{
RemoveFromVerticallyAdjacentBoxes(box, 1, pencilMarks, digit, result);
}
if (columns[0] == 0 && columns[1] == 0 && columns[2] > 0)
{
RemoveFromVerticallyAdjacentBoxes(box, 2, pencilMarks, digit, result);
}
if (rows[0] > 0 && rows[1] == 0 && rows[2] == 0)
{
RemoveFromHorizontallyAdjacentBoxes(box, 0, pencilMarks, digit, result);
}
if (rows[0] == 0 && rows[1] > 0 && rows[2] == 0)
{
RemoveFromHorizontallyAdjacentBoxes(box, 1, pencilMarks, digit, result);
}
if (rows[0] == 0 && rows[1] == 0 && rows[2] > 0)
{
RemoveFromHorizontallyAdjacentBoxes(box, 2, pencilMarks, digit, result);
}
}
}
}
return(result);
}
