public void CheckPredecessorLineGraph()
{
AdjacencyGraph g = new AdjacencyGraph(true);
IVertex v1 = g.AddVertex();
IVertex v2 = g.AddVertex();
IVertex v3 = g.AddVertex();
IEdge e12 = g.AddEdge(v1, v2);
IEdge e23 = g.AddEdge(v2, v3);
EdgeDoubleDictionary weights = DijkstraShortestPathAlgorithm.UnaryWeightsFromEdgeList(g);
DijkstraShortestPathAlgorithm dij = new DijkstraShortestPathAlgorithm(g, weights);
PredecessorRecorderVisitor vis = new PredecessorRecorderVisitor();
dij.RegisterPredecessorRecorderHandlers(vis);
dij.Compute(v1);
EdgeCollection col = vis.Path(v2);
Assert.AreEqual(1, col.Count);
Assert.AreEqual(e12, col[0]);
col = vis.Path(v3);
Assert.AreEqual(2, col.Count);
Assert.AreEqual(e12, col[0]);
Assert.AreEqual(e23, col[1]);
}
/// <summary>
/// Computes a set of eulerian trail, starting at <paramref name="s"/>
/// that spans the entire graph.
/// </summary>
/// <remarks>
/// <para>
/// This method computes a set of eulerian trail starting at <paramref name="s"/>
/// that spans the entire graph.The algorithm outline is as follows:
/// </para>
/// <para>
/// The algorithms iterates throught the Eulerian circuit of the augmented
/// graph (the augmented graph is the graph with additional edges to make
/// the number of odd vertices even).
/// </para>
/// <para>
/// If the current edge is not temporary, it is added to the current trail.
/// </para>
/// <para>
/// If the current edge is temporary, the current trail is finished and
/// added to the trail collection. The shortest path between the
/// start vertex <paramref name="s"/> and the target vertex of the
/// temporary edge is then used to start the new trail. This shortest
/// path is computed using the <see cref="BreadthFirstSearchAlgorithm"/>.
/// </para>
/// </remarks>
/// <param name="s">start vertex</param>
/// <returns>eulerian trail set, all starting at s</returns>
/// <exception cref="ArgumentNullException">s is a null reference.</exception>
/// <exception cref="Exception">Eulerian trail not computed yet.</exception>
public EdgeCollectionCollection Trails(IVertex s)
{
if (s == null)
{
throw new ArgumentNullException("s");
}
if (this.Circuit.Count == 0)
{
throw new Exception("Circuit is empty");
}
// find the first edge in the circuit.
int i = 0;
for (i = 0; i < this.Circuit.Count; ++i)
{
IEdge e = this.Circuit[i];
if (TemporaryEdges.Contains(e))
{
continue;
}
if (e.Source == s)
{
break;
}
}
if (i == this.Circuit.Count)
{
throw new Exception("Did not find vertex in eulerian trail?");
}
// create collections
EdgeCollectionCollection trails = new EdgeCollectionCollection();
EdgeCollection trail = new EdgeCollection();
BreadthFirstSearchAlgorithm bfs =
new BreadthFirstSearchAlgorithm(VisitedGraph);
PredecessorRecorderVisitor vis = new PredecessorRecorderVisitor();
bfs.RegisterPredecessorRecorderHandlers(vis);
bfs.Compute(s);
// go throught the edges and build the predecessor table.
int start = i;
for (; i < this.Circuit.Count; ++i)
{
IEdge e = this.Circuit[i];
if (TemporaryEdges.Contains(e))
{
// store previous trail and start new one.
if (trail.Count != 0)
{
trails.Add(trail);
}
// start new trail
// take the shortest path from the start vertex to
// the target vertex
trail = vis.Path(e.Target);
}
else
{
trail.Add(e);
}
}
// starting again on the circuit
for (i = 0; i < start; ++i)
{
IEdge e = this.Circuit[i];
if (TemporaryEdges.Contains(e))
{
// store previous trail and start new one.
if (trail.Count != 0)
{
trails.Add(trail);
}
// start new trail
// take the shortest path from the start vertex to
// the target vertex
trail = vis.Path(e.Target);
}
else
{
trail.Add(e);
}
}
// adding the last element
if (trail.Count != 0)
{
trails.Add(trail);
}
return(trails);
}
