// Dijkstra's algorithm.
private bool search()
{
// KeyHeap is used as a heap that sorts indices
// based on the elements at their locations in
// accumulativeWeights.
KeyHeap<double> cheapestNodesHeap =
new KeyHeap<double>(
HeapSorting.Min,
accumulativeWeights,
numNodes
);
cheapestNodesHeap.Insert(src);
while (!cheapestNodesHeap.IsEmpty)
{
int cheapestNode = cheapestNodesHeap.Remove();
shortestPathTree[cheapestNode] = edgeFrontier[cheapestNode];
if (cheapestNode == tgt)
return true;
foreach (Edge e in g.EdgesFromNode(cheapestNode))
{
double weight = accumulativeWeights[cheapestNode] + e.Weight;
if (edgeFrontier[e.NodeTo] == null)
{
accumulativeWeights[e.NodeTo] = weight;
cheapestNodesHeap.Insert(e.NodeTo);
edgeFrontier[e.NodeTo] = e;
}
else if (weight < accumulativeWeights[e.NodeTo] && shortestPathTree[e.NodeTo] == null)
{
accumulativeWeights[e.NodeTo] = weight;
cheapestNodesHeap.Reorder(e.NodeTo);
edgeFrontier[e.NodeTo] = e;
}
}
}
// If no target was specified (or target did not exist) search
// returns false. The instance still holds valuable info though
// in the shortest path tree and the accumulative weights.
return false;
}
// The A* search.
private bool search()
{
// KeyHeap is used as a heap that sorts indices
// based on the elements at their locations in
// weightsPlusHeuristic.
KeyHeap<double> cheapestNodesHeap =
new KeyHeap<double>(
HeapSorting.Min,
weightsPlusHeuristic,
numNodes
);
cheapestNodesHeap.Insert(src);
while (!cheapestNodesHeap.IsEmpty)
{
int cheapestNode = cheapestNodesHeap.Remove();
shortestPathTree[cheapestNode] = edgeFrontier[cheapestNode];
if (cheapestNode == tgt)
return true;
foreach (Edge e in g.EdgesFromNode(cheapestNode))
{
double actualWeight = weights[cheapestNode] + e.Weight;
double heuristicWeight = actualWeight + heuristic(g, e.NodeTo, tgt);
if (edgeFrontier[e.NodeTo] == null)
{
weights[e.NodeTo] = actualWeight;
weightsPlusHeuristic[e.NodeTo] = heuristicWeight; // Heuristic weight, not actual!
cheapestNodesHeap.Insert(e.NodeTo);
edgeFrontier[e.NodeTo] = e;
}
else if (actualWeight < weights[e.NodeTo] && shortestPathTree[e.NodeTo] == null)
{
weights[e.NodeTo] = actualWeight;
weightsPlusHeuristic[e.NodeTo] = heuristicWeight; // Heuristic weight, not actual!
cheapestNodesHeap.Reorder(e.NodeTo);
edgeFrontier[e.NodeTo] = e;
}
}
}
return false;
}