public Track(Track PreviousTrack, Arc Transition)
{
if (_Target==null) throw new InvalidOperationException("You must specify a target Node for the Track class.");
Queue = PreviousTrack;
_Cost = Queue.Cost + Transition.Cost;
_NbArcsVisited = Queue._NbArcsVisited + 1;
EndNode = Transition.EndNode;
}
public Track(Node GraphNode)
{
if ( _Target==null ) throw new InvalidOperationException("You must specify a target Node for the Track class.");
_Cost = 0;
_NbArcsVisited = 0;
Queue = null;
EndNode = GraphNode;
}
private void Propagate(Track TrackToPropagate)
{
foreach ( Arc A in TrackToPropagate.EndNode.OutgoingArcs )
{
if ( A.Passable && A.EndNode.Passable )
{
Track Successor = new Track(TrackToPropagate, A);
int PosNF = _Closed.IndexOf(Successor, SameNodesReached);
int PosNO = _Open.IndexOf(Successor, SameNodesReached);
if ( PosNF>0 && Successor.Cost>=((Track)_Closed[PosNF]).Cost ) continue;
if ( PosNO>0 && Successor.Cost>=((Track)_Open[PosNO]).Cost ) continue;
if ( PosNF>0 ) _Closed.RemoveAt(PosNF);
if ( PosNO>0 ) _Open.RemoveAt(PosNO);
_Open.Add(Successor);
}
}
}
private Node[] GoBackUpNodes(Track T)
{
int Nb = T.NbArcsVisited;
Node[] Path = new Node[Nb+1];
for (int i=Nb; i>=0; i--, T=T.Queue)
Path[i] = T.EndNode;
return Path;
}
/// <summary>
/// Use for a 'step by step' search only. This method is alternate to SearchPath.
/// The algorithm must have been initialize before.
/// </summary>
/// <exception cref="InvalidOperationException">You must initialize AStar before using NextStep().</exception>
/// <returns>'true' unless the search ended.</returns>
public bool NextStep()
{
if ( !Initialized ) throw new InvalidOperationException("You must initialize AStar before launching the algorithm.");
if ( _Open.Count==0 ) return false;
_NbIterations++;
int IndexMin = _Open.IndexOfMin();
Track BestTrack = (Track)_Open[IndexMin];
_Open.RemoveAt(IndexMin);
if ( BestTrack.Succeed )
{
_LeafToGoBackUp = BestTrack;
_Open.Clear();
}
else
{
Propagate(BestTrack);
_Closed.Add(BestTrack);
}
return _Open.Count>0;
}
/// <summary>
/// Use for a 'step by step' search only. This method is alternate to SearchPath.
/// Initializes AStar before performing search steps manually with NextStep.
/// </summary>
/// <exception cref="ArgumentNullException">StartNode and EndNode cannot be null.</exception>
/// <param name="StartNode">The node from which the path must start.</param>
/// <param name="EndNode">The node to which the path must end.</param>
public void Initialize(Node StartNode, Node EndNode)
{
if ( StartNode==null || EndNode==null ) throw new ArgumentNullException();
_Closed.Clear();
_Open.Clear();
Track.Target = EndNode;
_Open.Add( new Track(StartNode) );
_NbIterations = 0;
_LeafToGoBackUp = null;
}