internal static IEnumerable <IEnumerable <TNode> > FindOrderedItems(IEnumerable <TNode> database)
{
var seedEnumerator = database.GetEnumerator();
if (seedEnumerator.MoveNext())
{
var seedItem = new TreePredictableItem <TNode>(null, seedEnumerator);
var queue = new List <TreePredictableItem <TNode> > {
seedItem
};
while (queue.Count != 0)
{
var item = queue[0];
queue.RemoveAt(0);
if (item._isReal)
{
yield return(item);
if (item._enumerator.MoveNext())
{
var nextItem = new TreePredictableItem <TNode>(item._parent, item._enumerator);
nextItem.Enqueue(queue);
}
else
{
item._enumerator.Dispose();
}
if (1 < item._count)
{
item.MakePotential();
item.Enqueue(queue);
}
}
else
{
item.ExpandPotentialParent(queue);
}
}
}
}
private void ExpandPotentialParent(List <TreePredictableItem <TNode> > queue)
{
var item = this;
var done = false;
while (!done)
{
var node = item._node;
var enumerator = node.GetChildren().GetEnumerator();
if (enumerator.MoveNext())
{
var firstNode = enumerator.Current;
if (enumerator.MoveNext())
{
item = new TreePredictableItem <TNode>(item, enumerator);
item.Enqueue(queue);
done = true;
}
else
{
// Walking down single branch.
enumerator.Dispose();
item = new TreePredictableItem <TNode>(item, firstNode);
}
}
else
{
// No potential next node.
enumerator.Dispose();
done = true;
}
}
}