/// <summary>
/// Seed the second box.
///
/// This is more difficult, but still quick.
///
/// B2's 1st row can be any from B1's 2nd or 3rd
/// B2's 2nd row must include any remaining from B2's 3rd row, fill in with B1's 1st row
/// B2's 3rd row is all remaining
/// </summary>
public void SeedSecondBox()
{
var boxSize = PuzzleGrid.Size.BoxSize();
var puzzleSize = PuzzleGrid.Size.ToInt32();
var firstBoxUsed = CreateArray(boxSize, () => new PuzzleSet(PuzzleGrid.Size));
// load first box used values
foreach (var boxCell in Enumerable.Range(0, puzzleSize))
{
var cell = PuzzleBoxes[0][boxCell];
var cellValue = cell.Value
?? throw new Exception($"Cell at {cell.Coordinate} is null");
firstBoxUsed[cell.Coordinate.Row].Add(cellValue);
}
var usedByRow = CreateArray(boxSize, () => new PuzzleSet(PuzzleGrid.Size));
// chose values for first row of second box (from first box, second and third rows)
var firstRowPossibilities = new PuzzleSet(firstBoxUsed[1]);
firstRowPossibilities.UnionWith(firstBoxUsed[2]);
for (var i = 0; i < boxSize; i++)
{
var value = PickRandomValueFromPuzzleSet(firstRowPossibilities);
usedByRow[0].Add(value);
firstRowPossibilities.Remove(value);
}
// chose values for second row of the second box
var secondRowPossibilities = new PuzzleSet(firstBoxUsed[0]);
secondRowPossibilities.UnionWith(firstBoxUsed[2]);
secondRowPossibilities.ExceptWith(usedByRow[0]);
var thirdRowPossibilities = new PuzzleSet(firstBoxUsed[0]);
thirdRowPossibilities.UnionWith(firstBoxUsed[1]);
thirdRowPossibilities.ExceptWith(usedByRow[0]);
while (thirdRowPossibilities.Count > 3)
{
var value = PickRandomValueFromPuzzleSet(secondRowPossibilities);
usedByRow[1].Add(value);
secondRowPossibilities.Remove(value);
thirdRowPossibilities.Remove(value);
}
// Value for bottom row
secondRowPossibilities.ExceptWith(thirdRowPossibilities);
usedByRow[1].UnionWith(secondRowPossibilities);
usedByRow[2].UnionWith(thirdRowPossibilities);
// assign values to each row of the box
for (var row = 0; row < boxSize; row++)
{
for (var col = boxSize; col < 2 * boxSize; col++)
{
var value = PickRandomValueFromPuzzleSet(usedByRow[row]);
PuzzleGrid[new PuzzleCoordinate(row, col)] = Convert.ToByte(value);
usedByRow[row].Remove(value);
}
}
}