/// <summary>
/// Initializes an instance with the specified information.
/// </summary>
/// <param name="conclusions">All conclusions.</param>
/// <param name="views">All views.</param>
/// <param name="als1">The ALS 1.</param>
/// <param name="als2">The ALS 2.</param>
/// <param name="bridgeAls">The bridge ALS.</param>
/// <param name="xDigitsMask">The X digits mask.</param>
/// <param name="yDigitsMask">The Y digits mask.</param>
/// <param name="zDigitsMask">The Z digits mask.</param>
public AlsXyWingTechniqueInfo(
IReadOnlyList <Conclusion> conclusions, IReadOnlyList <View> views,
Als als1, Als als2, Als bridgeAls, short xDigitsMask, short yDigitsMask, short zDigitsMask)
: base(conclusions, views) =>
(Als1, Als2, BridgeAls, XDigitsMask, YDigitsMask, ZDigitsMask) = (als1, als2, bridgeAls, xDigitsMask, yDigitsMask, zDigitsMask);
public override void GetAll(IBag <TechniqueInfo> accumulator, IReadOnlyGrid grid)
{
var rccs = new List <(Als _left, Als _right, short _mask)>();
var alses = Als.GetAllAlses(grid).ToArray();
// Gather all RCCs.
for (int i = 0, length = alses.Length; i < length - 1; i++)
{
var als1 = alses[i];
var(_, _, mask1, map1, _, _) = als1;
for (int j = i + 1; j < length; j++)
{
var als2 = alses[j];
var(_, _, mask2, map2, _, _) = als2;
var map = map1 | map2;
if (map.AllSetsAreInOneRegion(out _) || map1.Overlaps(map2))
{
continue;
}
short mask = (short)(mask1 & mask2);
if (mask == 0)
{
continue;
}
short rccMask = 0;
foreach (int digit in mask.GetAllSets())
{
if ((map & CandMaps[digit]).AllSetsAreInOneRegion(out _))
{
rccMask |= (short)(1 << digit);
}
}
if (rccMask == 0)
{
continue;
}
rccs.Add((als1, als2, rccMask));
}
}
// Now check them.
for (int i = 0, count = rccs.Count; i < count - 1; i++)
{
var(als11, als12, mask1) = rccs[i];
for (int j = i + 1; j < count; j++)
{
var(als21, als22, mask2) = rccs[j];
if (mask1 == mask2 && mask1.IsPowerOfTwo() && mask2.IsPowerOfTwo())
{
// Cannot form a XY-Wing.
continue;
}
if (!(als11 == als21 ^ als12 == als22 || als11 == als22 ^ als12 == als21))
{
continue;
}
// Get the logical order of three ALSes.
var(a, b, c) = true switch
{
_ when als11 == als21 => (als12, als22, als11),
_ when als11 == als22 => (als12, als21, als11),
_ when als12 == als21 => (als11, als22, als12),
_ => (als11, als21, als12)
};
var(_, aRegion, aMask, aMap, _, _) = a;
var(_, bRegion, bMask, bMap, _, _) = b;
var(_, cRegion, _, cMap, _, _) = c;
var map = aMap | bMap;
if (map == aMap || map == bMap)
{
continue;
}
if (!_allowOverlapping && (aMap.Overlaps(bMap) || aMap.Overlaps(cMap) || bMap.Overlaps(cMap)))
{
continue;
}
foreach (int digit1 in mask1.GetAllSets())
{
foreach (int digit2 in mask2.GetAllSets())
{
if (digit1 == digit2)
{
continue;
}
short finalX = (short)(1 << digit1);
short finalY = (short)(1 << digit2);
short digitsMask = (short)(aMask & bMask & ~(finalX | finalY));
if (digitsMask == 0)
{
continue;
}
// Gather eliminations.
short finalZ = 0;
var conclusions = new List <Conclusion>();
foreach (int digit in digitsMask.GetAllSets())
{
var elimMap = (
((aMap | bMap) & CandMaps[digit]).PeerIntersection
& CandMaps[digit]) - (aMap | bMap | cMap);
if (elimMap.IsEmpty)
{
continue;
}
finalZ |= (short)(1 << digit);
foreach (int cell in elimMap)
{
conclusions.Add(new Conclusion(Elimination, cell, digit));
}
}
if (conclusions.Count == 0)
{
continue;
}
// Record highlight candidates and cells.
var cellOffsets = new List <(int, int)>();
var candidateOffsets = new List <(int, int)>();
foreach (int cell in aMap)
{
short mask = grid.GetCandidatesReversal(cell);
short alsDigitsMask = (short)(mask & ~(finalX | finalZ));
short xDigitsMask = (short)(mask & (finalX));
short zDigitsMask = (short)(mask & finalZ);
foreach (int digit in alsDigitsMask.GetAllSets())
{
candidateOffsets.Add((-1, cell * 9 + digit));
}
foreach (int digit in xDigitsMask.GetAllSets())
{
candidateOffsets.Add((1, cell * 9 + digit));
}
foreach (int digit in zDigitsMask.GetAllSets())
{
candidateOffsets.Add((2, cell * 9 + digit));
}
}
foreach (int cell in bMap)
{
short mask = grid.GetCandidatesReversal(cell);
short alsDigitsMask = (short)(mask & ~(finalY | finalZ));
short yDigitsMask = (short)(mask & finalY);
short zDigitsMask = (short)(mask & finalZ);
foreach (int digit in alsDigitsMask.GetAllSets())
{
candidateOffsets.Add((-1, cell * 9 + digit));
}
foreach (int digit in yDigitsMask.GetAllSets())
{
candidateOffsets.Add((1, cell * 9 + digit));
}
foreach (int digit in zDigitsMask.GetAllSets())
{
candidateOffsets.Add((2, cell * 9 + digit));
}
}
foreach (int cell in cMap)
{
short mask = grid.GetCandidatesReversal(cell);
short alsDigitsMask = (short)(mask & ~(finalX | finalY));
short xyDigitsMask = (short)(mask & (finalX | finalY));
foreach (int digit in alsDigitsMask.GetAllSets())
{
candidateOffsets.Add((-3, cell * 9 + digit));
}
foreach (int digit in xyDigitsMask.GetAllSets())
{
candidateOffsets.Add((1, cell * 9 + digit));
}
}
accumulator.Add(
new AlsXyWingTechniqueInfo(
conclusions,
views: new[]
/// <inheritdoc/>
public override void GetAll(IBag <TechniqueInfo> accumulator, IReadOnlyGrid grid)
{
var house = (Span <int>) stackalloc int[2];
var alses = Als.GetAllAlses(grid).ToArray();
for (int i = 0, length = alses.Length; i < length - 1; i++)
{
var als1 = alses[i];
var(isBivalue1, region1, mask1, map1, possibleElimMap1, _) = als1;
for (int j = i + 1; j < length; j++)
{
var als2 = alses[j];
var(isBivalue2, region2, mask2, map2, possibleElimMap2, _) = als2;
short xzMask = (short)(mask1 & mask2);
var map = map1 | map2;
var overlapMap = map1 & map2;
if (!_allowOverlapping && overlapMap.IsNotEmpty)
{
continue;
}
// Remove all digits to satisfy that the RCC digit cannot appear
// in the intersection of two ALSes.
if (overlapMap.IsNotEmpty)
{
foreach (int cell in overlapMap)
{
xzMask &= (short)~grid.GetCandidatesReversal(cell);
}
}
// If the number of digits that both two ALSes contain is only one (or zero),
// the ALS-XZ will not be formed.
if (xzMask.CountSet() < 2 || map.AllSetsAreInOneRegion(out int region))
{
continue;
}
short rccMask = 0, z = 0;
int nh = 0;
foreach (int digit in xzMask.GetAllSets())
{
if ((map & CandMaps[digit]).AllSetsAreInOneRegion(out region))
{
// 'digit' is the RCC digit.
rccMask |= (short)(1 << digit);
house[nh++] = region;
}
else
{
// 'digit' is the eliminating digit.
z |= (short)(1 << digit);
}
}
if (rccMask == 0 || rccMask.IsPowerOfTwo() && z == 0)
{
continue;
}
// Check basic eliminations.
bool? isDoublyLinked = false;
short finalZ = 0;
var conclusions = new List <Conclusion>();
foreach (int elimDigit in z.GetAllSets())
{
var elimMap = (CandMaps[elimDigit] & map).PeerIntersection & CandMaps[elimDigit];
if (elimMap.IsEmpty)
{
continue;
}
foreach (int cell in elimMap)
{
conclusions.Add(new Conclusion(Elimination, cell, elimDigit));
}
finalZ |= (short)(1 << elimDigit);
}
if (_allowAlsCycles && rccMask.CountSet() == 2)
{
// Doubly linked ALS-XZ.
isDoublyLinked = true;
foreach (int elimDigit in (z & ~rccMask).GetAllSets())
{
var zMap = CandMaps[elimDigit] & map1;
if (zMap.IsEmpty)
{
continue;
}
var elimMap = zMap.PeerIntersection & CandMaps[elimDigit] & map2;
if (elimMap.IsEmpty)
{
continue;
}
finalZ |= (short)(1 << elimDigit);
}
// RCC digit 2 eliminations.
int k = 0;
foreach (int digit in rccMask.GetAllSets())
{
var elimMap = (RegionMaps[house[k]] & CandMaps[digit]) - map;
if (elimMap.IsNotEmpty)
{
foreach (int cell in elimMap)
{
if (grid.Exists(cell, digit) is true)
{
conclusions.Add(new Conclusion(Elimination, cell, digit));
}
}
}
k++;
}
// Possible eliminations.
var tempMap = map;
tempMap = CandMaps[mask1.FindFirstSet()];
for (k = 1; k < mask1.CountSet(); k++)
{
tempMap |= CandMaps[mask1.SetAt(k)];
}
tempMap &= possibleElimMap1;
if (tempMap.IsNotEmpty)
{
foreach (int cell in tempMap)
{
foreach (int digit in
(grid.GetCandidatesReversal(cell) & (mask1 & ~rccMask)).GetAllSets())
{
conclusions.Add(new Conclusion(Elimination, cell, digit));
}
}
}
tempMap = CandMaps[mask2.FindFirstSet()];
for (k = 1; k < mask2.CountSet(); k++)
{
tempMap |= CandMaps[mask2.SetAt(k)];
}
tempMap &= possibleElimMap2;
if (tempMap.IsNotEmpty)
{
foreach (int cell in tempMap)
{
foreach (int digit in
(grid.GetCandidatesReversal(cell) & (mask2 & ~rccMask)).GetAllSets())
{
conclusions.Add(new Conclusion(Elimination, cell, digit));
}
}
}
}
if (conclusions.Count == 0)
{
continue;
}
// Now record highlight elements.
bool isEsp = als1.IsBivalueCell || als2.IsBivalueCell;
var candidateOffsets = new List <(int, int)>();
var cellOffsets = new List <(int, int)>();
if (isEsp)
{
foreach (int cell in map)
{
foreach (int digit in grid.GetCandidatesReversal(cell).GetAllSets())
{
candidateOffsets.Add((finalZ >> digit & 1, cell * 9 + digit));
}
}
}
else
{
foreach (int cell in map1)
{
short mask = grid.GetCandidatesReversal(cell);
short alsDigitsMask = (short)(mask & ~(finalZ | rccMask));
short targetDigitsMask = (short)(mask & finalZ);
short rccDigitsMask = (short)(mask & rccMask);
foreach (int digit in alsDigitsMask.GetAllSets())
{
candidateOffsets.Add((-1, cell * 9 + digit));
}
foreach (int digit in targetDigitsMask.GetAllSets())
{
candidateOffsets.Add((2, cell * 9 + digit));
}
foreach (int digit in rccDigitsMask.GetAllSets())
{
candidateOffsets.Add((1, cell * 9 + digit));
}
}
foreach (int cell in map2)
{
short mask = grid.GetCandidatesReversal(cell);
short alsDigitsMask = (short)(mask & ~(finalZ | rccMask));
short targetDigitsMask = (short)(mask & finalZ);
short rccDigitsMask = (short)(mask & rccMask);
foreach (int digit in alsDigitsMask.GetAllSets())
{
candidateOffsets.Add((-2, cell * 9 + digit));
}
foreach (int digit in targetDigitsMask.GetAllSets())
{
candidateOffsets.Add((2, cell * 9 + digit));
}
foreach (int digit in rccDigitsMask.GetAllSets())
{
candidateOffsets.Add((1, cell * 9 + digit));
}
}
}
accumulator.Add(
new AlsXzTechniqueInfo(
conclusions,
views: new[]
/// <summary>
/// Initializes an instance with the specified information.
/// </summary>
/// <param name="conclusions">All conclusions.</param>
/// <param name="views">All views.</param>
/// <param name="als1">The ALS 1 used.</param>
/// <param name="als2">The ALS 2 used.</param>
/// <param name="xDigitsMask">The X digits mask.</param>
/// <param name="zDigitsMask">The Z digits mask.</param>
/// <param name="isDoublyLinked">Indicates whether the instance is a doubly linked ALS-XZ.</param>
public AlsXzTechniqueInfo(
IReadOnlyList <Conclusion> conclusions, IReadOnlyList <View> views, Als als1,
Als als2, short xDigitsMask, short zDigitsMask, bool?isDoublyLinked) : base(conclusions, views) =>
(Als1, Als2, XDigitsMask, ZDigitsMask, IsDoublyLinked) = (als1, als2, xDigitsMask, zDigitsMask, isDoublyLinked);
/// <inheritdoc/>
public override void GetAll(IBag <TechniqueInfo> accumulator, IReadOnlyGrid grid)
{
var alses = Als.GetAllAlses(grid).ToArray();
// Gather all conjugate pairs.
var conjugatePairs = new ICollection <ConjugatePair>?[9];
for (int digit = 0; digit < 9; digit++)
{
for (int region = 0; region < 27; region++)
{
var temp = RegionMaps[region] & CandMaps[digit];
if (temp.Count != 2)
{
continue;
}
(conjugatePairs[digit] ??= new List <ConjugatePair>()).Add(new ConjugatePair(temp, digit));
}
}
// Iterate on each ALS.
for (int i = 0, length = alses.Length; i < length - 1; i++)
{
var als1 = alses[i];
var(_, region1, mask1, map1, _, _) = als1;
for (int j = i + 1; j < length; j++)
{
var als2 = alses[j];
var(_, region2, mask2, map2, _, _) = als2;
if (map1.Overlaps(map2) || (map1 | map2).AllSetsAreInOneRegion(out _))
{
continue;
}
short mask = (short)(mask1 & mask2);
if (mask.CountSet() < 2)
{
continue;
}
foreach (int x in mask.GetAllSets())
{
if ((conjugatePairs[x]?.Count ?? 0) == 0)
{
continue;
}
var p1 = (map1 & CandMaps[x]).PeerIntersection & CandMaps[x];
var p2 = (map2 & CandMaps[x]).PeerIntersection & CandMaps[x];
if (p1.IsEmpty || p2.IsEmpty)
{
// At least one of two ALSes cannot see the node of the conjugate pair.
continue;
}
// Iterate on each conjugate pair.
short wDigitsMask = 0;
var conclusions = new List <Conclusion>();
foreach (var conjugatePair in conjugatePairs[x] ?? Array.Empty <ConjugatePair>())
{
var cpMap = conjugatePair.Map;
if (cpMap.Overlaps(map1) || cpMap.Overlaps(map2))
{
// Conjugate pair cannot overlap with the ALS structure.
continue;
}
if ((cpMap & p1).Count != 1 || (cpMap & p2).Count != 1 || ((p1 | p2) & cpMap).Count != 2)
{
continue;
}
foreach (int w in (mask & ~(1 << x)).GetAllSets())
{
var tempMap = ((map1 | map2) & CandMaps[w]).PeerIntersection & CandMaps[w];
if (tempMap.IsEmpty)
{
continue;
}
wDigitsMask |= (short)(1 << w);
foreach (int cell in tempMap)
{
conclusions.Add(new Conclusion(Elimination, cell, w));
}
}
if (conclusions.Count == 0)
{
continue;
}
// Record highlight cell and candidate offsets.
var cellOffsets = new List <(int, int)>();
cellOffsets.AddRange(from cell in map1 select(-1, cell));
cellOffsets.AddRange(from cell in map2 select(-2, cell));
var candidateOffsets = new List <(int, int)>
{
(0, cpMap.SetAt(0) * 9 + x), (0, cpMap.SetAt(1) * 9 + x)
};
foreach (int cell in map1)
{
foreach (int digit in grid.GetCandidatesReversal(cell).GetAllSets())
{
candidateOffsets.Add((
true switch
{
_ when digit == x => 1,
_ when(wDigitsMask >> digit & 1) != 0 => 2,
_ => - 1
},
/// <summary>
/// Initializes an instance with the specified information.
/// </summary>
/// <param name="conclusions">All conclusions.</param>
/// <param name="views">All views.</param>
/// <param name="als1">The ALS 1.</param>
/// <param name="als2">The ALS 2.</param>
/// <param name="conjugatePair">The conjugate pair.</param>
/// <param name="wDigitsMask">The W digits mask.</param>
/// <param name="x">The X digit.</param>
public AlsWWingTechniqueInfo(
IReadOnlyList <Conclusion> conclusions, IReadOnlyList <View> views,
Als als1, Als als2, ConjugatePair conjugatePair, short wDigitsMask, int x) : base(conclusions, views) =>
(Als1, Als2, ConjugatePair, WDigitsMask, XDigit) = (als1, als2, conjugatePair, wDigitsMask, x);