public static bool IsBilocationRegion(this IReadOnlyGrid @this, int digit, int region, out short mask)
{
if (@this.HasDigitValue(digit, region))
{
mask = 0;
return(false);
}
mask = @this.GetDigitAppearingMask(digit, region);
return(mask.CountSet() == 2);
}
/// <summary>
/// Searches all basic fish of the specified size.
/// </summary>
/// <param name="accumulator">The result accumulator.</param>
/// <param name="grid">The grid.</param>
/// <param name="size">The size.</param>
/// <param name="searchRow">
/// Indicates the solver will searching rows or columns.
/// </param>
/// <returns>The result.</returns>
private static void AccumulateAllBySize(
IBag <TechniqueInfo> accumulator, IReadOnlyGrid grid, int size, bool searchRow)
{
int baseSetStart = searchRow ? 9 : 18;
int coverSetStart = searchRow ? 18 : 9;
var baseSets2 = (Span <int>) stackalloc int[2];
var coverSets2 = (Span <int>) stackalloc int[2];
var baseSets3 = (Span <int>) stackalloc int[3];
var coverSets3 = (Span <int>) stackalloc int[3];
var baseSets4 = (Span <int>) stackalloc int[4];
var coverSets4 = (Span <int>) stackalloc int[4];
for (int digit = 0; digit < 9; digit++)
{
for (int bs1 = baseSetStart; bs1 < baseSetStart + 10 - size; bs1++)
{
// Get the appearing mask of 'digit' in 'bs1'.
short baseMask1 = grid.GetDigitAppearingMask(digit, bs1);
if (baseMask1.CountSet() < 2)
{
continue;
}
for (int bs2 = bs1 + 1; bs2 < baseSetStart + 11 - size; bs2++)
{
// Get the appearing mask of 'digit' in 'bs2'.
short baseMask2 = grid.GetDigitAppearingMask(digit, bs2);
if (baseMask2.CountSet() < 2)
{
continue;
}
if (size == 2)
{
short baseMask = (short)(baseMask1 | baseMask2);
int finAndBodyCount = baseMask.CountSet();
if (finAndBodyCount >= 5)
{
continue;
}
// Search (Finned) (Sashimi) X-Wing.
for (int cs1 = coverSetStart, i = 0; cs1 < coverSetStart + 8; cs1++, i++)
{
// Check whether this cover set has 'digit'.
if ((baseMask >> i & 1) == 0)
{
continue;
}
for (int cs2 = cs1 + 1, j = i + 1; cs2 < coverSetStart + 9; cs2++, j++)
{
// Check whether this cover set has 'digit'.
if ((baseMask >> j & 1) == 0)
{
continue;
}
// Confirm all elimination cells.
baseSets2[0] = bs1;
baseSets2[1] = bs2;
coverSets2[0] = cs1;
coverSets2[1] = cs2;
var bodyMap = GridMap.Empty;
var elimMap = GridMap.Empty;
GetGridMap(ref bodyMap, baseSets2, CandMaps[digit]);
GetGridMap(ref elimMap, coverSets2, CandMaps[digit]);
bodyMap &= elimMap;
elimMap -= bodyMap;
// Check the existence of fin.
var finCellsMap = GridMap.Empty;
if (finAndBodyCount == 2) // size == 2
{
goto Label_CheckWhetherTheNumberOfIntersectionCellsIsNotZero;
}
// Confirm all fin cells.
short finMask = (short)(baseMask & ~(1 << i | 1 << j) & 511);
foreach (int baseSet in baseSets2)
{
foreach (int x in finMask.GetAllSets())
{
int possibleFinCellOffset = RegionCells[baseSet][x];
if (CandMaps[digit][possibleFinCellOffset])
{
finCellsMap.Add(possibleFinCellOffset);
}
}
}
// Check the number of fins is less than 3.
if (finCellsMap.Count > 2)
{
continue;
}
// And all fins do not lie on any cover sets.
var coverSetsMap = GridMap.Empty;
foreach (int coverSet in coverSets2)
{
coverSetsMap |= RegionMaps[coverSet];
}
if (coverSetsMap.Overlaps(finCellsMap))
{
continue;
}
// Get intersection.
foreach (int finCell in finCellsMap)
{
elimMap &= new GridMap(finCell);
}
Label_CheckWhetherTheNumberOfIntersectionCellsIsNotZero:
// Check whether the number of intersection cells is not 0.
if (elimMap.IsNotEmpty)
{
// Finned/Sashimi X-Wing found.
// Check eliminations.
var conclusions = new List <Conclusion>();
foreach (int offset in elimMap)
{
conclusions.Add(new Conclusion(Elimination, offset * 9 + digit));
}
if (conclusions.Count == 0)
{
continue;
}
// Eliminations does exist.
// Check all highlight candidates.
var candidateOffsets = new List <(int, int)>();
foreach (int cell in bodyMap)
{
candidateOffsets.Add((0, cell * 9 + digit));
}
if (finCellsMap.IsNotEmpty)
{
foreach (int cell in finCellsMap)
{
candidateOffsets.Add((1, cell * 9 + digit));
}
}
// Check the fish is sashimi, normal finned or normal.
bool?isSashimi = null;
if (finCellsMap.IsNotEmpty)
{
isSashimi = true;
int finCell = finCellsMap.SetAt(0);
int block = finCell / 9 / 3 * 3 + finCell % 9 / 3;
foreach (int offset in bodyMap)
{
if (offset / 9 / 3 * 3 + offset % 9 / 3 == block)
{
isSashimi = false;
break;
}
}
}
accumulator.Add(
new NormalFishTechniqueInfo(
conclusions,
views: new[]
/// <inheritdoc/>
public override void GetAll(IBag <TechniqueInfo> accumulator, IReadOnlyGrid grid)
{
for (int digit = 0; digit < 9; digit++)
{
for (int r1 = 0; r1 < 26; r1++)
{
for (int r2 = r1 + 1; r2 < 27; r2++)
{
// Get masks.
short mask1 = grid.GetDigitAppearingMask(digit, r1);
short mask2 = grid.GetDigitAppearingMask(digit, r2);
if (mask1.CountSet() != 2 || mask2.CountSet() != 2)
{
continue;
}
// Get all cells.
var map1 = GridMap.Empty;
var map2 = GridMap.Empty;
var cells1 = new List <int>();
var cells2 = new List <int>();
foreach (int pos1 in mask1.GetAllSets())
{
int cell1 = RegionCells[r1][pos1];
cells1.Add(cell1);
map1.Add(cell1);
}
foreach (int pos2 in mask2.GetAllSets())
{
int cell2 = RegionCells[r2][pos2];
cells2.Add(cell2);
map2.Add(cell2);
}
if ((map1 & map2).IsNotEmpty)
{
continue;
}
// Check two cells share a same region.
int sameRegion;
int headIndex, tailIndex, c1Index, c2Index;
for (int i = 0; i < 2; i++)
{
int cell1 = cells1[i];
for (int j = 0; j < 2; j++)
{
int cell2 = cells2[j];
if (new GridMap {
cell1, cell2
}.AllSetsAreInOneRegion(out sameRegion))
{
(c1Index, c2Index, headIndex, tailIndex) = (i, j, i == 0 ? 1 : 0, j == 0 ? 1 : 0);
goto Label_Checking;
}
}
}
// Not same block.
continue;
Label_Checking:
// Two strong link found.
// Record all eliminations.
int head, tail;
head = cells1[headIndex];
tail = cells2[tailIndex];
var conclusions = new List <Conclusion>();
var gridMap = new GridMap(head, false) & new GridMap(tail, false) & CandMaps[digit];
if (gridMap.IsEmpty)
{
continue;
}
foreach (int cell in gridMap)
{
conclusions.Add(new Conclusion(Elimination, cell, digit));
}
if (conclusions.Count == 0)
{
continue;
}
accumulator.Add(
new TwoStrongLinksTechniqueInfo(
conclusions,
views: new[]