private void ReduceRegion(int skip, SudokuRegion region, SudokuState state, ICollection <IEvent> events)
{
var quad = 0u;
buffer.Clear();
foreach (var index in region.Skip(skip))
{
var value = state[index];
if (SudokuCell.Count(value) < 4)
{
quad |= value;
// Joined the represent more then 3 values.
if (SudokuCell.Count(quad) > 4 || buffer.Count > 3)
{
return;
}
buffer.Add(index);
}
}
if (buffer.Count == 4)
{
Fetch(quad, buffer, region, state, events);
}
}
/// <summary>Reduced a cell by excluding the options of the other.</summary>
public ReduceResult AndMask(int index, uint mask)
{
unchecked
{
var val = m_Values[index];
var nw = val & mask;
m_Values[index] = nw;
if (nw == SudokuPuzzle.Invalid)
{
return(ReduceResult.Inconsistent);
}
if (SudokuCell.Count(nw) == 1 && SudokuCell.Count(val) != 1)
{
Unknowns--;
if (IsSolved)
{
return(ReduceResult.Solved | ReduceResult.Reduced | ReduceResult.Found);
}
return(ReduceResult.Reduced | ReduceResult.Found);
}
return(val != nw ? ReduceResult.Reduced : ReduceResult.None);
}
}
private void ReduceRegion(SudokuRegion region, SudokuState state, ICollection <IEvent> events)
{
var nakedPair = 0u;
var count = 0;
foreach (var index in region)
{
var value = state[index];
// nothing found yet.
if (nakedPair == default)
{
if (SudokuCell.Count(value) == 2)
{
nakedPair = value;
count++;
}
}
// Equal to the first (potential) naked pair.
else if (value == nakedPair && count++ > 2)
{
throw new InvalidPuzzleException();
}
}
if (count > 1)
{
Fetch(nakedPair, region, state, events);
}
}
public ReduceHiddenPairs()
{
for (var f = 1; f <= 8; f++)
{
for (var s = f + 1; s <= 9; s++)
{
Pairs.Add(SudokuCell.Single(f) | SudokuCell.Single(s));
}
}
}
/// <summary>Reduced a cell by excluding the options of the other.</summary>
public IEvent And <TSolver>(int index, uint mask)
{
unchecked
{
var val = m_Values[index];
var nw = val & mask;
m_Values[index] = nw;
if (nw == SudokuPuzzle.Invalid)
{
throw new InvalidPuzzleException();
}
if (SudokuCell.Count(nw) == 1 && SudokuCell.Count(val) != 1)
{
return(ValueFound.Ctor <TSolver>(index, nw));
}
return(val != nw ? ReducedOption.Instance : (IEvent)NoReduction.Instance);
}
}
/// <summary>Gets the number of optional values for a given index of the Sudoku state.</summary> public int Count(int index) => SudokuCell.Count(m_Values[index]);