public IEnumerable <TravelPath> findCheapestFirePaths(int startLocation)
{
//reduction: want to find chepest path that include edge with fire
// insert node "inside" the fire edges and calculate the distance to it
//in order to get the right the path insert "opposite" edge inside the fire edge
//with cost infinity.
//edges between real node and virtual node will be with original cost
TravelGraph reductionGraph = createWorldWithClearWays();
List <int> fireNodes = new List <int>();
int generatePlace = reductionGraph.Vertices.Max();
Dictionary <int, int> virtualToRealPlace = new Dictionary <int, int>();
foreach (var edge in _fireWays)
{
var newNodeTarget = ++generatePlace;
reductionGraph.AddVertex(newNodeTarget);
var newNodeSource = ++generatePlace;
reductionGraph.AddVertex(newNodeSource);
reductionGraph.AddEdge(new TravelEdge(edge.Source, newNodeTarget), _graph.GetCost(edge));
reductionGraph.AddEdge(new TravelEdge(newNodeSource, edge.Target), _graph.GetCost(edge));
//opposite edge
virtualToRealPlace.Add(newNodeTarget, edge.Target);
virtualToRealPlace.Add(newNodeSource, edge.Source);
reductionGraph.AddEdge(new TravelEdge(newNodeSource, newNodeTarget), double.MaxValue);
fireNodes.Add(newNodeSource);
fireNodes.Add(newNodeTarget);
}
var paths = reductionGraph.findChepestPaths(startLocation, fireNodes.ToArray()).ToArray();
foreach (var path in paths)
{
foreach (var virt in virtualToRealPlace.Keys)
{
path.Replace(virt, virtualToRealPlace[virt]);
}
}
return(paths);
}
public void AddPlace(int place)
{
_graph.AddVertex(place);
}
