public void Enqueue(T item)
{
RandomMeldablePriorityTree <T> node;
if (_dictionary.TryGetValue(item, out node))
{
_tree = _tree.DecreaseKey(node, item);
}
else
{
node = new RandomMeldablePriorityTree <T>(item);
_tree = RandomMeldablePriorityTree <T> .Meld(_tree, node);
}
_dictionary[item] = node;
}
/// <summary>
/// Returns the best path.
/// TPosition will be used as a dictionary key.
/// </summary>
/// <param name="getNeighbors">Given a position, return all the neighbors directly accessible from that position.</param>
public static List <TNode> FindMinimalPath <TNode, TPosition>(
TNode startingNode,
Func <Dictionary <TPosition, RandomMeldablePriorityTree <TNode> >, TNode, bool> isDone,
Func <TNode, IEnumerable <TNode> > getNeighbors)
where TNode : SearchNodeBase <TPosition>
{
TNode best;
var lookup = new Dictionary <TPosition, RandomMeldablePriorityTree <TNode> >();
var opens = new RandomMeldablePriorityTree <TNode>(startingNode);
do
{
var lowest = opens.Element;
// for dual direction, change this ending situation to be a lambda.
// spawn two instances of the search method
// in their lambda to see if they're done see if their position passed
// exists in the lookup table here (and is open)
// if that happens they are both done
if (isDone.Invoke(lookup, lowest))
{
best = lowest;
break;
}
opens = opens.DeleteMin();
#if DEBUG
if (opens != null && opens.Parent != null)
{
throw new InvalidOperationException("Expected opens to always point to the root.");
}
#endif
lookup[lowest.Position] = null; // keep this below the isDone check
foreach (var neighbor in getNeighbors.Invoke(lowest))
{
RandomMeldablePriorityTree <TNode> existing;
if (lookup.TryGetValue(neighbor.Position, out existing))
{
if (existing == null)
{
continue;
}
opens = opens.DecreaseKey(existing, neighbor);
}
else
{
existing = new RandomMeldablePriorityTree <TNode>(neighbor);
opens = RandomMeldablePriorityTree <TNode> .Meld(opens, existing);
lookup[neighbor.Position] = existing;
}
}
if (opens == null)
{
best = lowest;
break;
}
} while (true);
LastExpansionCount = lookup.Count;
var ret = new List <TNode>();
while (best != null)
{
ret.Add(best);
best = best.Parent as TNode;
}
ret.Reverse();
return(ret);
}