public void testStronglyConnected4() {
DefaultDirectedGraph<Integer, String> graph =
new DefaultDirectedGraph<Integer, String>(
new EdgeFactory<Integer, String>() {
public String createEdge(Integer from, Integer to) {
return (from + "->" + to).intern();
}
});
new RingGraphGenerator<Integer, String>(3)
.generateGraph(
graph,
new VertexFactory<Integer>() {
private int i = 0;
public Integer createVertex() {
return i++;
}
},
null);
StrongConnectivityInspector<Integer, String> sc =
new StrongConnectivityInspector<Integer, String>(graph);
Set<Set<Integer>> expected = new HashSet<Set<Integer>>();
expected.add(graph.vertexSet());
assertEquals(expected, new HashSet<Set<Integer>>(sc.stronglyConnectedSets()));
}
/**
* Finds the vertex set for the subgraph of all cycles.
*
* @return set of all vertices which participate in at least one cycle in this graph
*/
public Set<V> findCycles() {
// ProbeIterator can't be used to handle this case,
// so use StrongConnectivityInspector instead.
StrongConnectivityInspector<V, E> inspector = new StrongConnectivityInspector<V, E>(graph);
List<Set<V>> components = inspector.stronglyConnectedSets();
// A vertex participates in a cycle if either of the following is
// true: (a) it is in a component whose size is greater than 1
// or (b) it is a self-loop
Set<V> set = new HashSet<V>();
for (Set<V> component : components) {
if (component.size() > 1) {
// cycle
set.addAll(component);
} else {
V v = component.iterator().next();
if (graph.containsEdge(v, v)) {
// self-loop
set.add(v);
}
}
}
return set;
}
/** . */
public void testStronglyConnected3() {
DirectedGraph<String, DefaultEdge> g =
new DefaultDirectedGraph<String, DefaultEdge>(DefaultEdge.class);
g.addVertex(V1);
g.addVertex(V2);
g.addVertex(V3);
g.addVertex(V4);
g.addEdge(V1, V2);
g.addEdge(V2, V3);
g.addEdge(V3, V1); // strongly connected
g.addEdge(V1, V4);
g.addEdge(V2, V4);
g.addEdge(V3, V4); // weakly connected
StrongConnectivityInspector<String, DefaultEdge> inspector =
new StrongConnectivityInspector<String, DefaultEdge>(g);
// convert from List to Set because we need to ignore order
// during comparison
Set<Set<String>> actualSets = new HashSet<Set<String>>(inspector.stronglyConnectedSets());
// construct the expected answer
Set<Set<String>> expectedSets = new HashSet<Set<String>>();
Set<String> set = new HashSet<String>();
set.add(V1);
set.add(V2);
set.add(V3);
expectedSets.add(set);
set = new HashSet<String>();
set.add(V4);
expectedSets.add(set);
assertEquals(expectedSets, actualSets);
actualSets.clear();
List<DirectedSubgraph<String, DefaultEdge>> subgraphs = inspector.stronglyConnectedSubgraphs();
for (DirectedSubgraph<String, DefaultEdge> sg : subgraphs) {
actualSets.add(sg.vertexSet());
StrongConnectivityInspector<String, DefaultEdge> ci =
new StrongConnectivityInspector<String, DefaultEdge>(sg);
assertTrue(ci.isStronglyConnected());
}
assertEquals(expectedSets, actualSets);
}