public static Graph LabelCorrecting(Graph g, int vert)
{
Output.WriteLine("[Label Correcting Output]");
//Not working, I think because of the two loops for in and out edges
//Change this to assume g is an undirected graph
//Keep a heap of vertices, based on their distance label
//Each one is initially infinity, except the intial vertex, which is 0
Graph copy = new Graph();
Graph tree = new Graph();
//Create a copy to preserve g's state
g.CopyTo(copy);
List <Vertex> vertices = copy.GetVertices();
List <Edge> edges = copy.GetEdges();
DijkstraData v = new DijkstraData();
v.Predecessor = null;
v.InQ = false;
v.V = vertices[vert];
v.D = 0;
v.InTree = false;
v.EdgeLength = float.PositiveInfinity;
vertices[vert].Tag = v;
Heap <DijkstraData> q = new Heap <DijkstraData>(true);
q.Add(vertices[vert].Tag as DijkstraData);
(vertices[vert].Tag as DijkstraData).InQ = true;
foreach (Vertex u in vertices)
{
if (!v.V.Equals(u))
{
DijkstraData dd = new DijkstraData();
dd.D = float.PositiveInfinity;
dd.V = u;
dd.InTree = false;
dd.InQ = false;
u.Tag = dd;
}
}
float maxEdgeWeight = float.NegativeInfinity;
foreach (Edge e in edges)
{
if (Math.Abs(e.Weight) > maxEdgeWeight)
{
maxEdgeWeight = Math.Abs(e.Weight);
}
}
int n = vertices.Count;
float negativeCycleCheck = n * -maxEdgeWeight;
while (q.HasNext())
{
DijkstraData dd = q.Next();
dd.InQ = false;
/*if (dd.Predecessor == null)
* {
* tree.AddVertex(dd.V);
* }
* else
* {
* tree.AddEdge(new Edge(dd.Predecessor, dd.V, dd.EdgeLength));
* dd.InTree = true;
* }*/
foreach (Edge e in dd.V.GetOutEdges())
{
Vertex connectedVertex = e.GetToVertex();
DijkstraData data = connectedVertex.Tag as DijkstraData;
if (data.D > dd.D + e.Weight)
{
data.D = dd.D + e.Weight;
if (data.D < negativeCycleCheck)
{
throw new Exception("Negative cycle detected!");
}
data.Predecessor = dd.V;
if (!q.Contains(data))
{
q.Add(data);
data.InQ = true;
}
}
}
if (g.Directed)
{
continue;
}
foreach (Edge e in dd.V.GetInEdges())
{
Vertex connectedVertex = e.GetFromVertex();
DijkstraData data = connectedVertex.Tag as DijkstraData;
if (data.D > dd.D + e.Weight)
{
data.D = dd.D + e.Weight;
if (data.D < negativeCycleCheck)
{
throw new Exception("Negative cycle detected!");
}
data.Predecessor = dd.V;
if (!q.Contains(data))
{
q.Add(data);
data.InQ = true;
}
}
}
}
Output.WriteLine("Distance from selected vertex to:");
foreach (Vertex vertex in vertices)
{
Output.WriteLine(vertex.ToString() + " = " + (vertex.Tag as DijkstraData).D);
}
Output.WriteLine("[End Label Correcting Output]");
return(tree);
}
public static Graph Dijkstra(Graph g, int vert, bool directed)
{
Output.WriteLine("[Dijkstra Output]");
//If I get a negative edge weight, tell user to use label correcting instead of dijkstra's
//Change this to assume g is an undirected graph
//Keep a heap of vertices, based on their distance label
//Each one is initially infinity, except the intial vertex, which is 0
Graph copy = new Graph();
Graph tree = new Graph();
//Create a copy to preserve g's state
g.CopyTo(copy);
List <Vertex> vertices = copy.GetVertices();
List <Edge> edges = copy.GetEdges();
DijkstraData v = new DijkstraData();
v.Predecessor = null;
v.InQ = false;
v.V = vertices[vert];
v.D = 0;
v.InTree = false;
v.EdgeLength = float.PositiveInfinity;
vertices[vert].Tag = v;
Heap <DijkstraData> q = new Heap <DijkstraData>(true);
q.Add(vertices[vert].Tag as DijkstraData);
(vertices[vert].Tag as DijkstraData).InQ = true;
foreach (Vertex u in vertices)
{
if (!v.V.Equals(u))
{
DijkstraData dd = new DijkstraData();
dd.D = float.PositiveInfinity;
dd.V = u;
dd.InTree = false;
u.Tag = dd;
q.Add(dd);
dd.InQ = true;
}
}
foreach (Edge e in edges)
{
if (e.Weight < 0)
{
Output.WriteLine("Negative edge weight detected. Use Label Correcting instead of Dijkstra");
return(null);
}
}
while (q.HasNext())
{
DijkstraData dd = q.Next();
dd.InQ = false;
/*if (dd.Predecessor == null)
* {
* tree.AddVertex(dd.V);
* dd.InTree = true;
* }
* else
* {
* tree.AddEdge(new Edge(dd.Predecessor, dd.V, dd.EdgeLength));
* dd.InTree = true;
* }*/
foreach (Edge e in dd.V.GetOutEdges())
{
Vertex connectedVertex = e.GetToVertex();
DijkstraData data = connectedVertex.Tag as DijkstraData;
if (data.InQ)
{
if (dd.D + e.Weight < data.D)
{
if (dd.D + e.Weight < data.D)
{
data.D = dd.D + e.Weight;
q.Update(data);
}
}
}
}
//If this is a directed graph, don't consider in edges
if (directed)
{
continue;
}
foreach (Edge e in dd.V.GetInEdges())
{
Vertex connectedVertex = e.GetFromVertex();
DijkstraData data = connectedVertex.Tag as DijkstraData;
if (data.InQ)
{
if (dd.D + e.Weight < data.D)
{
data.D = dd.D + e.Weight;
q.Update(data);
}
}
}
}
Output.WriteLine("Distance from selected vertex to:");
foreach (Vertex vertex in vertices)
{
Output.WriteLine(vertex.ToString() + " = " + (vertex.Tag as DijkstraData).D);
}
Output.WriteLine("[End Dijkstra Output]");
return(tree);
}
