private IEnumerable <Solution> Cover(int k, SearchData searchData)
{
try
{
if (k == 0)
{
RaiseStarted();
}
if (IsCancelled())
{
RaiseCancelled();
yield break;
}
RaiseSearchStep(searchData.IterationCount, searchData.CurrentSolution.RowIndexes);
searchData.IncrementIterationCount();
if (MatrixIsEmpty(searchData.Root))
{
if (searchData.CurrentSolution.RowIndexes.Any())
{
searchData.IncrementSolutionCount();
var solutionIndex = searchData.SolutionCount - 1;
var solution = searchData.CurrentSolution;
RaiseSolutionFound(solution, solutionIndex);
yield return(solution);
}
yield break;
}
var c = ChooseColumnWithLeastRows(searchData.Root);
CoverColumn(c);
for (var r = c.Down; r != c; r = r.Down)
{
if (IsCancelled())
{
RaiseCancelled();
yield break;
}
searchData.PushCurrentSolutionRowIndex(r.RowIndex);
for (var j = r.Right; j != r; j = j.Right)
{
CoverColumn(j.ListHeader);
}
var recursivelyFoundSolutions = Cover(k + 1, searchData);
foreach (var solution in recursivelyFoundSolutions)
{
yield return(solution);
}
for (var j = r.Left; j != r; j = j.Left)
{
UncoverColumn(j.ListHeader);
}
searchData.PopCurrentSolutionRowIndex();
}
UncoverColumn(c);
}
finally
{
if (k == 0)
{
RaiseFinished();
}
}
}