public IEnumerable <SudokuBoard> Solve()
{
ResetSolutions();
SudokuProgress simplify = SudokuProgress.PROGRESS;
while (simplify == SudokuProgress.PROGRESS)
{
simplify = Simplify();
}
if (simplify == SudokuProgress.FAILED)
{
yield break;
}
// Find one of the values with the least number of alternatives, but that still has at least 2 alternatives
var query = from rule in rules
from tile in rule
where tile.PossibleCount > 1
orderby tile.PossibleCount ascending
select tile;
SudokuTile chosen = query.FirstOrDefault();
if (chosen == null)
{
// We solved it!
yield return(this);
yield break;
}
foreach (var value in Enumerable.Range(1, _maxValue))
{
// Iterate through all the valid possibles on the chosen square and pick a number for it
if (!chosen.IsPossibleValue(value))
{
continue;
}
var copy = new SudokuBoard(this);
copy.Tile(chosen.X, chosen.Y).Fix(value, "Trial and error");
foreach (var innerSolution in copy.Solve())
{
yield return(innerSolution);
}
}
yield break;
}
internal SudokuProgress Simplify()
{
SudokuProgress result = SudokuProgress.NO_PROGRESS;
bool valid = CheckValid();
if (!valid)
{
return(SudokuProgress.FAILED);
}
foreach (SudokuRule rule in rules)
{
result = SudokuTile.CombineSolvedState(result, rule.Solve());
}
return(result);
}