public void Solve()
{
BasicSolve();
if (IsLegal && !IsSolved)
{
var undeterminedCells =
MatrixIterator
.Where(cell => !cell.IsDetermined);
SudokuCell speculationTarget = undeterminedCells
.First(cell => cell.Candidates.Count ==
undeterminedCells.Min(c => c.Candidates.Count));
Random rng = new Random();
var shuffledCandidates = speculationTarget.Candidates
.OrderBy(c => rng.Next());
foreach (int candidate in shuffledCandidates)
{
SudokuBoard speculativeBoard = new SudokuBoard(this);
speculativeBoard.SetCell(
cellRow: speculationTarget.Row,
cellColumn: speculationTarget.Column,
valueToSet: candidate);
speculativeBoard.Solve();
if (speculativeBoard.IsLegal && speculativeBoard.IsSolved)
{
this.Copy(speculativeBoard);
return;
}
}
}
}
public async Task ParallelSolve(int branchingDepth = -1)
{
if (branchingDepth == 0)
{
Solve();
return;
}
BasicSolve();
if (IsLegal && !IsSolved)
{
var undeterminedCells =
MatrixIterator
.Where(cell => !cell.IsDetermined);
SudokuCell speculationTarget = undeterminedCells
.First(cell => cell.Candidates.Count ==
undeterminedCells.Min(c => c.Candidates.Count));
var tokenSource = new CancellationTokenSource();
List <Task <SudokuBoard> > speculationTasks = new List <Task <SudokuBoard> >();
foreach (int candidate in speculationTarget.Candidates)
{
SudokuBoard speculativeBoard = new SudokuBoard(this);
speculativeBoard.SetCell(
cellRow: speculationTarget.Row,
cellColumn: speculationTarget.Column,
valueToSet: candidate);
var token = tokenSource.Token;
speculationTasks.Add(
Task.Factory.StartNew(() =>
{
speculativeBoard
.ParallelSolve(branchingDepth > 0 ? branchingDepth - 1 : branchingDepth)
.Wait(token);
return(speculativeBoard);
},
token)
);
}
while (speculationTasks.Count > 0)
{
Task <SudokuBoard> completedTask = await Task.WhenAny(speculationTasks);
SudokuBoard speculativeBoard = completedTask.Result;
if (speculativeBoard.IsLegal && speculativeBoard.IsSolved)
{
tokenSource.Cancel();
this.Copy(speculativeBoard);
return;
}
speculationTasks.Remove(completedTask);
}
}
}
public void RecomputeCandidates()
{
MatrixIterator
.Where(cell => !cell.IsDetermined)
.ToList()
.ForEach(cell => cell.Clear());
MatrixIterator
.Where(cell => cell.IsDetermined)
.ToList()
.ForEach(cell => UpdateBoardCandidates(
sourceRow: cell.Row,
sourceColumn: cell.Column,
valueToRemove: (int)cell.Value));
}
public int SetNakedCandidateCells()
{
int nCellsSet = 0;
MatrixIterator
.Where(cell => cell.HasNakedCandidate())
.ToList()
.ForEach(
cell =>
{
if (cell.Candidates.Count == 1)
{
SetCell(
cellRow: cell.Row,
cellColumn: cell.Column,
valueToSet: cell.Candidates.First());
nCellsSet++;
}
});
return(nCellsSet);
}