// for performance comparison, compute connected components serially
public Collection<Collection<Node<E>>> getCCSerially(UndirectedGraph<E> graph) {
// node is one of the elements of nodes, nodes is a subset of dg's
// nodes
Queue<Node<E>> q = new LinkedList<Node<E>>();
Collection<Node<E>> nodes = graph.getAllNodes();
// hashmap to store the nodes, whose children have been visited
HashMap<Node<E>, Integer> hashmap = new HashMap<Node<E>, Integer>(nodes.size());
Iterator<Node<E>> itr = nodes.iterator();
Collection<Node<E>> cc;
Node<E> temp;
Node<E> currentRoot;
while (itr.hasNext()) {
cc = new Vector<Node<E>>(INIT_SIZE_FOR_CC);
currentRoot = itr.next();
if (hashmap.get(currentRoot) != null) // the children already
// been
// visited
continue;
q.add(currentRoot);
while (!q.isEmpty()) {
temp = q.poll(); // temp' children definitely not visited
cc.add(temp);
hashmap.put(temp, 1); // temp's childrent been visited now
Collection<AdjacentNode<E>> collection = graph.getLinkedNodes(temp);
if (collection == null) continue;
Iterator<AdjacentNode<E>> innerIter = collection.iterator();
while (innerIter.hasNext()) {
Node<E> toEnqueue = innerIter.next().getNode();
if (hashmap.get(toEnqueue) == null) // toEnqueue's
// children
// not benn visited yet
q.add(toEnqueue);
}
}
if (cc.size() > 1) ccs.add(cc);
else cc = null;
}
return ccs;
}
