private SudokuGridCell FindFirstCellWithMinimumCandidates(SudokuGrid grid)
{
byte minCandidates = grid.Metrics.MaximumNumber;
SudokuGridCell minCandidatesCell = null;
grid.IterateLinesXY((x, y) =>
{
var currCell = grid.Cells[y, x];
if (currCell.Candidates != null &&
currCell.Candidates.Count < minCandidates)
{
minCandidates = (byte)currCell.Candidates.Count;
minCandidatesCell = currCell;
}
});
return minCandidatesCell;
}
private SudokuGridCell[,] MakeAssumptionInCell(ref SudokuGridPosition? minCandidatesCellPos)
{
if (!minCandidatesCellPos.HasValue)
{
// TODO: optimize: lookup that kind of cell repetitively when its number of candidates changes (decreases): compare against the minimum value from a variable (where to put it?)
minCandidatesCellPos = FindFirstCellWithMinimumCandidates(Grid).Position;
}
var minCandidatesCell = Grid.Cells[minCandidatesCellPos.Value.Y, minCandidatesCellPos.Value.X];
byte assumedNumber = minCandidatesCell.Candidates.ToArray()[0];
assumptionsGrid = (SudokuGrid)Grid.GetType()
.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic,
null, CallingConventions.HasThis, new[] { typeof(SudokuGridConstraints) }, null)
.Invoke(new [] { (object)Grid.Constraints });
// BUG: !!! as we use the standard grid here, which was not initially intended to be used anywhere except for decode-and-construct scenarios, by the time we reach this code the assumptionsGrid's cells are not initialized yet -- consider introducing some sort of temporary 'grid' (most probably, a kind of 'cells-only layer'). For that reason one of the ctor's code sections was moved into the Reset() method
var assumptionsGridSolver = new SudokuSolvingIterationAssumptionTechnique(assumptionsGrid);
// WI: cell-to-cell iteration is a very intensive process -- use cells array cloning instead with targeted minCandidatesCell... altering
var minCandidatesCellPosCopy = minCandidatesCellPos.Value;
assumptionsGrid.IterateLinesXY((x, y) =>
{
SudokuGridCell currCell;
var currPos = new SudokuGridPosition(x, y, false);
if (currPos.Equals(minCandidatesCellPosCopy))
{
currCell = new SudokuGridCell(assumptionsGrid, currPos, assumedNumber);
assumptionsGridSolver.lastFilledPos = currPos;
assumptionsGridSolver.currCheckingPos = currPos;
assumptionsGridSolver.currCheckingPos.Shift(1, assumptionsGrid.Metrics);
}
else
{
currCell = new SudokuGridCell(assumptionsGrid, currPos, Grid.Cells[y, x].Number);
if (currCell.Candidates != null)
{
// just to bring into accord with the latest value from the 'parent' grid
currCell.Candidates.IntersectWith(Grid.Cells[y, x].Candidates);
}
}
SudokuGrid.AssignNewCell(assumptionsGrid, currCell);
//assumptionsGrid.Cells[y, x] = currCell;
});
//List<SudokuGridCell[,]> assumptionGridSolutuons = assumptionGridSolver.SearchSolutions();
//if (assumptionGridSolutuons.Count > 0) // correct assumption was made
//{
// return assumptionsGrid.Cells;
//}
//SudokuGridCell[,] solution;
if (assumptionsGridSolver.SearchSolutionDebug()) // correct assumption was made
{
//return solution;
return assumptionsGrid.Cells;
}
// incorrect assumption was made (executes on contradiction only)
minCandidatesCell.Candidates.Remove(assumedNumber);
// if there were only two candidates, with assumedNumber being one of them, then the remaining one is a clue
if (minCandidatesCell.IsClue)
{
minCandidatesCellPos = null;
var newPos = new SudokuGridPosition(minCandidatesCell.Position.X, minCandidatesCell.Position.Y, false);
lastFilledPos = newPos;
currCheckingPos = newPos;
currCheckingPos.Shift(1, Grid.Metrics);
}
return null;
}
public static byte[] ToBinary(SudokuGrid grid, SudokuConvertionAlgorithm algorithm)
{
var sb = new StringBuilder(grid.Metrics.CellsTotal);
grid.IterateLinesXY((x, y) => sb.Append(grid.Cells[y, x].Number));
return ToBinary(sb.ToString(), algorithm, grid.Constraints, grid.Metrics);
}
