/// <summary>
/// Computes the set of eulerian trails that traverse the edge set.
/// </summary>
/// <remarks>
/// This method returns a set of disjoint eulerian trails. This set
/// of trails spans the entire set of edges.
/// </remarks>
/// <returns>Eulerian trail set</returns>
public EdgeCollectionCollection Trails()
{
EdgeCollectionCollection trails = new EdgeCollectionCollection();
EdgeCollection trail = new EdgeCollection();
foreach (IEdge e in this.Circuit)
{
if (TemporaryEdges.Contains(e))
{
// store previous trail and start new one.
if (trail.Count != 0)
{
trails.Add(trail);
}
// start new trail
trail = new EdgeCollection();
}
else
{
trail.Add(e);
}
}
if (trail.Count != 0)
{
trails.Add(trail);
}
return(trails);
}
/// <summary>
/// Returns the minimal set of path from the entry point that
/// executes all actions
/// </summary>
/// <returns></returns>
public EdgeCollectionCollection AllPaths()
{
EdgeCollectionCollection es = new EdgeCollectionCollection();
foreach (IEdge e in EndPathEdges)
{
es.Add(Path(e));
}
return(es);
}
/// <summary>
/// Returns the minimal set of path from the entry point that
/// executes all actions
/// </summary>
/// <returns></returns>
public EdgeCollectionCollection AllPaths()
{
EdgeCollectionCollection es = new EdgeCollectionCollection();
foreach (IVertex v in EndPathVertices)
{
es.Add(Path(v));
}
return(es);
}
/// <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);
}
