private void NextGeneration(int parentID)
{
Node parent = new Node();
parent = Stations[parentID];
List <Node> children = new List <Node>();
children = MetroNetwork.GenChildren(parent); // generates list of neighbouring nodes
int index;
// nondeterministic element:
Shuffle(children); // mixes up children so that different ones are selected first each time
foreach (var child in children)
{
index = child.StationId;
child.Score = Stations[index].Score;
if (child.UpdateScore(parent, OriginStationId)) // returns true only if it is a valid forwards step
{
Stations[index].CopyLineBranchIndexFrom(child); // must only edit location when sure new route is faster
Stations[index].Score = child.Score; // assign new score
Enqueue(index); // adds this stationId onto list of stations to visit
}
}
}
// basic methods
internal void RewindUntilOrigin(List <Node> stations) // retraces steps from destination to origin
{
Path.AddLast(stations[DestinationId]);
int index;
bool ongoing = true;
int parentCount;
Random rand = new Random();
List <Node> neighbours = new List <Node>();
List <int> validParentIds = new List <int>();
do
{
neighbours = MetroNetwork.GenChildren(Path.First());
foreach (Node n in neighbours)
{
index = n.StationId;
if (Path.First().ValidRewind(stations[index], OriginId))
{
validParentIds.Add(index);
}
}
parentCount = validParentIds.Count();
if (parentCount > 0)
{
index = validParentIds[rand.Next(parentCount)]; // goes down a random path
AddOn(stations[index]);
if (index == OriginId) // terminates when reached origin
{
ongoing = false;
}
}
else // there are no valid ancestors >> no route exists (disconnected graph)
{
ongoing = false;
}
validParentIds.Clear();
neighbours.Clear();
} while (ongoing);
}