/** @see java.util.Iterator#hasNext() */
public boolean hasNext() {
if (startVertex != null) {
encounterStartVertex();
}
if (isConnectedComponentExhausted()) {
if (state == CCS_WITHIN_COMPONENT) {
state = CCS_AFTER_COMPONENT;
if (nListeners != 0) {
fireConnectedComponentFinished(ccFinishedEvent);
}
}
if (isCrossComponentTraversal()) {
while (vertexIterator.hasNext()) {
V v = vertexIterator.next();
if (!isSeenVertex(v)) {
encounterVertex(v, null);
state = CCS_BEFORE_COMPONENT;
return true;
}
}
return false;
} else {
return false;
}
} else {
return true;
}
}
/** @see Graph#getAllEdges(Object, Object) */
public Set<E> getAllEdges(V sourceVertex, V targetVertex) {
Set<E> edges = null;
if (containsVertex(sourceVertex) && containsVertex(targetVertex)) {
edges = new ArrayUnenforcedSet<E>();
Iterator<E> iter = getEdgeContainer(sourceVertex).vertexEdges.iterator();
while (iter.hasNext()) {
E e = iter.next();
boolean equalStraight =
sourceVertex.equals(getEdgeSource(e)) && targetVertex.equals(getEdgeTarget(e));
boolean equalInverted =
sourceVertex.equals(getEdgeTarget(e)) && targetVertex.equals(getEdgeSource(e));
if (equalStraight || equalInverted) {
edges.add(e);
}
}
}
return edges;
}
/**
* Creates a new iterator for the specified graph. Iteration will start at the specified start
* vertex. If the specified start vertex is <code>
* null</code>, Iteration will start at an arbitrary graph vertex.
*
* @param g the graph to be iterated.
* @param startVertex the vertex iteration to be started.
* @throws IllegalArgumentException if <code>g==null</code> or does not contain <code>startVertex
* </code>
*/
public CrossComponentIterator(Graph<V, E> g, V startVertex) {
super();
if (g == null) {
throw new IllegalArgumentException("graph must not be null");
}
graph = g;
specifics = createGraphSpecifics(g);
vertexIterator = g.vertexSet().iterator();
setCrossComponentTraversal(startVertex == null);
reusableEdgeEvent = new FlyweightEdgeEvent<V, E>(this, null);
reusableVertexEvent = new FlyweightVertexEvent<V>(this, null);
if (startVertex == null) {
// pick a start vertex if graph not empty
if (vertexIterator.hasNext()) {
this.startVertex = vertexIterator.next();
} else {
this.startVertex = null;
}
} else if (g.containsVertex(startVertex)) {
this.startVertex = startVertex;
} else {
throw new IllegalArgumentException("graph must contain the start vertex");
}
}
/**
* Compute the unique decomposition of the input graph G (atoms of G). Implementation of algorithm
* Atoms as described in Berry et al. (2010), DOI:10.3390/a3020197, <a
* href="http://www.mdpi.com/1999-4893/3/2/197">http://www.mdpi.com/1999-4893/3/2/197</a>
*/
private void computeAtoms() {
if (chordalGraph == null) {
computeMinimalTriangulation();
}
separators = new HashSet<>();
// initialize g' as subgraph of graph (same vertices and edges)
UndirectedGraph<V, E> gprime = copyAsSimpleGraph(graph);
// initialize h' as subgraph of chordalGraph (same vertices and edges)
UndirectedGraph<V, E> hprime = copyAsSimpleGraph(chordalGraph);
atoms = new HashSet<>();
Iterator<V> iterator = meo.descendingIterator();
while (iterator.hasNext()) {
V v = iterator.next();
if (generators.contains(v)) {
Set<V> separator = new HashSet<>(Graphs.neighborListOf(hprime, v));
if (isClique(graph, separator)) {
if (separator.size() > 0) {
if (separators.contains(separator)) {
fullComponentCount.put(separator, fullComponentCount.get(separator) + 1);
} else {
fullComponentCount.put(separator, 2);
separators.add(separator);
}
}
UndirectedGraph<V, E> tmpGraph = copyAsSimpleGraph(gprime);
tmpGraph.removeAllVertices(separator);
ConnectivityInspector<V, E> con = new ConnectivityInspector<>(tmpGraph);
if (con.isGraphConnected()) {
throw new RuntimeException("separator did not separate the graph");
}
for (Set<V> component : con.connectedSets()) {
if (component.contains(v)) {
gprime.removeAllVertices(component);
component.addAll(separator);
atoms.add(new HashSet<>(component));
assert (component.size() > 0);
break;
}
}
}
}
hprime.removeVertex(v);
}
if (gprime.vertexSet().size() > 0) {
atoms.add(new HashSet<>(gprime.vertexSet()));
}
}
/** @see Graph#getEdge(Object, Object) */
public E getEdge(V sourceVertex, V targetVertex) {
if (containsVertex(sourceVertex) && containsVertex(targetVertex)) {
DirectedEdgeContainer<V, E> ec = getEdgeContainer(sourceVertex);
Iterator<E> iter = ec.outgoing.iterator();
while (iter.hasNext()) {
E e = iter.next();
if (getEdgeTarget(e).equals(targetVertex)) {
return e;
}
}
}
return null;
}
/**
* This method will check whether the graph passed in is Eulerian or not.
*
* @param g The graph to be checked
* @return true for Eulerian and false for non-Eulerian
*/
public static <V, E> boolean isEulerian(UndirectedGraph<V, E> g) {
// If the graph is not connected, then no Eulerian circuit exists
if (!(new ConnectivityInspector<V, E>(g)).isGraphConnected()) {
return false;
}
// A graph is Eulerian if and only if all vertices have even degree
// So, this code will check for that
Iterator<V> iter = g.vertexSet().iterator();
while (iter.hasNext()) {
V v = iter.next();
if ((g.degreeOf(v) % 2) == 1) {
return false;
}
}
return true;
}
/** @see Graph#getEdge(Object, Object) */
public E getEdge(V sourceVertex, V targetVertex) {
if (containsVertex(sourceVertex) && containsVertex(targetVertex)) {
Iterator<E> iter = getEdgeContainer(sourceVertex).vertexEdges.iterator();
while (iter.hasNext()) {
E e = iter.next();
boolean equalStraight =
sourceVertex.equals(getEdgeSource(e)) && targetVertex.equals(getEdgeTarget(e));
boolean equalInverted =
sourceVertex.equals(getEdgeTarget(e)) && targetVertex.equals(getEdgeSource(e));
if (equalStraight || equalInverted) {
return e;
}
}
}
return null;
}
/** @see Graph#getAllEdges(Object, Object) */
public Set<E> getAllEdges(V sourceVertex, V targetVertex) {
Set<E> edges = null;
if (containsVertex(sourceVertex) && containsVertex(targetVertex)) {
edges = new ArrayUnenforcedSet<E>();
DirectedEdgeContainer<V, E> ec = getEdgeContainer(sourceVertex);
Iterator<E> iter = ec.outgoing.iterator();
while (iter.hasNext()) {
E e = iter.next();
if (getEdgeTarget(e).equals(targetVertex)) {
edges.add(e);
}
}
}
return edges;
}
/**
* Updates outgoing vertices of the vertex. For each outgoing vertex, the new paths are obtained
* by concatenating the specified edge to the calculated paths of the specified vertex. If the
* weight of a new path is greater than the weight of any path stored so far at the outgoing
* vertex then the path is not added, otherwise it is added to the list of paths in increasing
* order of weight. Complexity =
*
* <ul>
* <li>O(<code>d(v)*k*(m+n)</code>) where <code>d(v)</code> is the outgoing degree of the
* specified vertex, <code>k</code> is the maximum number of shortest paths to compute,
* <code>m</code> is the number of edges of the graph and <code>n</code> is the number of
* vertices of the graph
* </ul>
*
* @param vertex
* @param improvedVertices
*/
private void updateOutgoingVertices(V vertex, Set<V> improvedVertices) {
// try to add new paths for the target vertices of the outgoing edges
// of the vertex in argument.
for (Iterator<E> iter = edgesOfIterator(vertex); iter.hasNext(); ) {
E edge = iter.next();
V vertexReachedByEdge = Graphs.getOppositeVertex(this.graph, edge, vertex);
// check if the path does not loop over the start vertex.
if (!vertexReachedByEdge.equals(this.startVertex)) {
if (this.seenDataContainer.containsKey(vertexReachedByEdge)) {
boolean relaxed = tryToAddNewPaths(vertexReachedByEdge, edge);
if (relaxed) {
improvedVertices.add(vertexReachedByEdge);
}
} else {
boolean relaxed = tryToAddFirstPaths(vertexReachedByEdge, edge);
if (relaxed) {
improvedVertices.add(vertexReachedByEdge);
}
}
}
}
}
/** {@inheritDoc} */
public void generateGraph(
Graph<V, E> target, VertexFactory<V> vertexFactory, Map<String, V> resultMap) {
if (size < 1) {
return;
}
// Add all the vertices to the set
for (int i = 0; i < size; i++) {
V newVertex = vertexFactory.createVertex();
target.addVertex(newVertex);
}
/*
* We want two iterators over the vertex set, one fast and one slow.
* The slow one will move through the set once. For each vertex,
* the fast iterator moves through the set, adding an edge to all
* vertices we haven't connected to yet.
*
* If we have an undirected graph, the second addEdge call will return
* nothing; it will not add a second edge.
*/
Iterator<V> slowI = target.vertexSet().iterator();
Iterator<V> fastI;
while (slowI.hasNext()) { // While there are more vertices in the set
V latestVertex = slowI.next();
fastI = target.vertexSet().iterator();
// Jump to the first vertex *past* latestVertex
while (fastI.next() != latestVertex) {;
}
// And, add edges to all remaining vertices
V temp;
while (fastI.hasNext()) {
temp = fastI.next();
target.addEdge(latestVertex, temp);
target.addEdge(temp, latestVertex);
}
}
}
/**
* This method will return a list of vertices which represents the Eulerian circuit of the graph.
*
* @param g The graph to find an Eulerian circuit
* @return null if no Eulerian circuit exists, or a list of vertices representing the Eulerian
* circuit if one does exist
*/
public static <V, E> List<V> getEulerianCircuitVertices(UndirectedGraph<V, E> g) {
// If the graph is not Eulerian then just return a null since no
// Eulerian circuit exists
if (!isEulerian(g)) {
return null;
}
// The circuit will be represented by a linked list
List<V> path = new LinkedList<V>();
UndirectedGraph<V, E> sg = new UndirectedSubgraph<V, E>(g, null, null);
path.add(sg.vertexSet().iterator().next());
// Algorithm for finding an Eulerian circuit Basically this will find an
// arbitrary circuit, then it will find another arbitrary circuit until
// every edge has been traversed
while (sg.edgeSet().size() > 0) {
V v = null;
// Find a vertex which has an edge that hasn't been traversed yet,
// and keep its index position in the circuit list
int index = 0;
for (Iterator<V> iter = path.iterator(); iter.hasNext(); index++) {
v = iter.next();
if (sg.degreeOf(v) > 0) {
break;
}
}
// Finds an arbitrary circuit of the current vertex and
// appends this into the circuit list
while (sg.degreeOf(v) > 0) {
for (Iterator<V> iter = sg.vertexSet().iterator(); iter.hasNext(); ) {
V temp = iter.next();
if (sg.containsEdge(v, temp)) {
path.add(index, temp);
sg.removeEdge(v, temp);
v = temp;
break;
}
}
}
}
return path;
}
