private static List<Edge> createPath(MyBreadthFirstIterator iter, Object endVertex) {
List<Edge> path = new ArrayList<Edge>();
while (true) {
Edge edge = iter.getSpanningTreeEdge(endVertex);
if (edge == null) {
break;
}
path.add(edge);
endVertex = edge.oppositeVertex(endVertex);
}
Collections.reverse(path);
return path;
}
private List lazyFindBiconnectedSets() {
if (biconnectedSets == null) {
biconnectedSets = new ArrayList();
Iterator connectedSets = new ConnectivityInspector(graph).connectedSets().iterator();
while (connectedSets.hasNext()) {
Set connectedSet = (Set) connectedSets.next();
if (connectedSet.size() == 1) {
continue;
}
Graph subgraph = new Subgraph(graph, connectedSet, null);
// do DFS
// Stack for the DFS
Stack vertexStack = new Stack();
Set visitedVertices = new HashSet();
Map parent = new HashMap();
List dfsVertices = new ArrayList();
Set treeEdges = new HashSet();
Object currentVertex = subgraph.vertexSet().toArray()[0];
vertexStack.push(currentVertex);
visitedVertices.add(currentVertex);
while (!vertexStack.isEmpty()) {
currentVertex = vertexStack.pop();
Object parentVertex = parent.get(currentVertex);
if (parentVertex != null) {
Edge edge = subgraph.getEdge(parentVertex, currentVertex);
// tree edge
treeEdges.add(edge);
}
visitedVertices.add(currentVertex);
dfsVertices.add(currentVertex);
Iterator edges = subgraph.edgesOf(currentVertex).iterator();
while (edges.hasNext()) {
// find a neighbour vertex of the current vertex
Edge edge = (Edge) edges.next();
if (!treeEdges.contains(edge)) {
Object nextVertex = edge.oppositeVertex(currentVertex);
if (!visitedVertices.contains(nextVertex)) {
vertexStack.push(nextVertex);
parent.put(nextVertex, currentVertex);
} else {
// non-tree edge
}
}
}
}
// DFS is finished. Now create the auxiliary graph h
// Add all the tree edges as vertices in h
SimpleGraph h = new SimpleGraph();
h.addAllVertices(treeEdges);
visitedVertices.clear();
Set connected = new HashSet();
for (Iterator it = dfsVertices.iterator(); it.hasNext(); ) {
Object v = it.next();
visitedVertices.add(v);
// find all adjacent non-tree edges
for (Iterator adjacentEdges = subgraph.edgesOf(v).iterator(); adjacentEdges.hasNext(); ) {
Edge l = (Edge) adjacentEdges.next();
if (!treeEdges.contains(l)) {
h.addVertex(l);
Object u = l.oppositeVertex(v);
// we need to check if (u,v) is a back-edge
if (!visitedVertices.contains(u)) {
while (u != v) {
Object pu = parent.get(u);
Edge f = subgraph.getEdge(u, pu);
h.addEdge(f, l);
if (!connected.contains(f)) {
connected.add(f);
u = pu;
} else {
u = v;
}
}
}
}
}
}
ConnectivityInspector connectivityInspector = new ConnectivityInspector(h);
biconnectedSets.addAll(connectivityInspector.connectedSets());
}
}
return biconnectedSets;
}