public static ShortestPathTree ShortestPathTree(Graph graph, String sourceLabel)
{
G.IDictionary <String, Node> nodes = graph.GetNodes();
if (!nodes.ContainsKey(sourceLabel))
{
throw new Exception("Source node not found in graph.");
}
ShortestPathTree predecessorTree = new ShortestPathTree(sourceLabel);
ISet <DijkstraNode> visited = new HashSet <DijkstraNode>();
java.util.PriorityQueue <DijkstraNode> pq = new java.util.PriorityQueue <DijkstraNode>();
foreach (String nodeLabel in nodes.Keys)
{
DijkstraNode newNode = new DijkstraNode(nodeLabel);
newNode.SetDist(double.MaxValue);
newNode.SetDepth(int.MaxValue);
predecessorTree.Add(newNode);
}
DijkstraNode sourceNode = predecessorTree.GetNodes()[predecessorTree.GetRoot()];
sourceNode.SetDist(0);
sourceNode.SetDepth(0);
pq.add(sourceNode, sourceNode.GetDist());
int count = 0;
while (!pq.isEmpty())
{
DijkstraNode current = pq.poll();
String currLabel = current.GetLabel();
visited.Add(current);
count++;
G.IDictionary <String, Double> neighbors = nodes[currLabel].GetNeighbors();
foreach (String currNeighborLabel in neighbors.Keys)
{
DijkstraNode neighborNode = predecessorTree.GetNodes()[currNeighborLabel];
Double currDistance = neighborNode.GetDist();
Double newDistance = current.GetDist() + nodes[currLabel].GetNeighbors()[currNeighborLabel];
if (newDistance < currDistance)
{
DijkstraNode neighbor = predecessorTree.GetNodes()[currNeighborLabel];
pq.remove(neighbor);
neighbor.SetDist(newDistance);
neighbor.SetDepth(current.GetDepth() + 1);
neighbor.SetParent(currLabel);
pq.add(neighbor, neighbor.GetDist());
}
}
}
return(predecessorTree);
}
// see comment at the top of the file regarding why the below Comparable<Vertex> methods has been removed
//public int compareTo(DijkstraNode comparedNode) {
// double distance1 = this.dist;
// double distance2 = comparedNode.getDist();
// if (distance1 == distance2)
// return 0;
// if (distance1 > distance2)
// return 1;
// return -1;
//}
//public int CompareTo(DijkstraNode other)
//{
// return compareTo(other);
//}
public bool Equals(DijkstraNode comparedNode)
{
return(this.GetLabel().Equals(comparedNode.GetLabel()));
}
public static Path ShortestPath(Graph graph, String sourceLabel, String targetLabel)
{
//if (!nodes.containsKey(sourceLabel))
// throw new Exception("Source node not found in graph.");
G.IDictionary <String, Node> nodes = graph.GetNodes();
ShortestPathTree predecessorTree = new ShortestPathTree(sourceLabel);
java.util.PriorityQueue <DijkstraNode> pq = new java.util.PriorityQueue <DijkstraNode>();
foreach (String nodeLabel in nodes.Keys)
{
DijkstraNode newNode = new DijkstraNode(nodeLabel);
newNode.SetDist(double.MaxValue);
newNode.SetDepth(int.MaxValue);
predecessorTree.Add(newNode);
}
DijkstraNode sourceNode = predecessorTree.GetNodes()[predecessorTree.GetRoot()];
sourceNode.SetDist(0);
sourceNode.SetDepth(0);
pq.add(sourceNode, sourceNode.GetDist());
int count = 0;
while (!pq.isEmpty())
{
DijkstraNode current = pq.poll();
String currLabel = current.GetLabel();
if (currLabel.Equals(targetLabel))
{
Path shortestPath = new Path();
String currentN = targetLabel;
String parentN = predecessorTree.GetParentOf(currentN);
while (parentN != null)
{
shortestPath.AddFirst(new Edge(parentN, currentN, nodes[parentN].GetNeighbors()[currentN]));
currentN = parentN;
parentN = predecessorTree.GetParentOf(currentN);
}
return(shortestPath);
}
count++;
G.IDictionary <String, Double> neighbors = nodes[currLabel].GetNeighbors();
foreach (String currNeighborLabel in neighbors.Keys)
{
DijkstraNode neighborNode = predecessorTree.GetNodes()[currNeighborLabel];
Double currDistance = neighborNode.GetDist();
Double newDistance = current.GetDist() + nodes[currLabel].GetNeighbors()[currNeighborLabel];
if (newDistance < currDistance)
{
DijkstraNode neighbor = predecessorTree.GetNodes()[currNeighborLabel];
pq.remove(neighbor);
neighbor.SetDist(newDistance);
neighbor.SetDepth(current.GetDepth() + 1);
neighbor.SetParent(currLabel);
pq.add(neighbor, neighbor.GetDist());
}
}
}
return(null);
}
public void Add(DijkstraNode newNode)
{
nodes.Add(newNode.GetLabel(), newNode);
}