internal bool DoesNotContain(PencilMarks pencilMarks, char digit)
{
for (int columnNumber = 0; columnNumber < 9; columnNumber++)
{
if (pencilMarks.HasMark(columnNumber, RowNumber, digit))
{
return(false);
}
}
return(true);
}
private void RemoveFromVerticallyAdjacentBoxes(Box box, int columnOffset, PencilMarks pencilMarks, char digit, List <string> results)
{
var columnNumber = box.Left + columnOffset;
for (int rowNumber = 0; rowNumber < box.Top; rowNumber++)
{
RemoveMark(pencilMarks, digit, results, columnNumber, rowNumber);
}
for (int rowNumber = box.Top + 3; rowNumber < 9; rowNumber++)
{
RemoveMark(pencilMarks, digit, results, columnNumber, rowNumber);
}
}
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> Reduce(Grid grid, PencilMarks pencilMarks)
{
var results = new List <string>();
var previousCount = -1;
while (results.Count > previousCount)
{
previousCount = results.Count;
foreach (var reducer in reducers)
{
results.AddRange(reducer.Evaluate(grid, pencilMarks));
}
}
return(results);
}
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);
}