public static List findCycles(DigraphIteration graph) {
ArrayStack stack = new ArrayStack();
ArrayStack path = new ArrayStack();
Set seen = new HashSet();
List cycles = new ArrayList();
Iterator vertexIterator = graph.vertexIterator();
while (vertexIterator.hasNext()) {
while (vertexIterator.hasNext()) {
Object vertex = vertexIterator.next();
if (seen.add(vertex)) {
stack.push(graph.outgoingIterator(vertex));
path.push(vertex);
break;
}
}
while (!stack.isEmpty()) {
ArcIterator i = (ArcIterator) stack.peek();
Object origin = i.getOrigin();
boolean subtreeIsTraversed = true;
while (i.hasNext()) {
i.next();
Object dst = i.getDestination();
int index = path.indexOf(dst);
if (index < 0) {
seen.add(dst);
stack.push(graph.outgoingIterator(dst));
path.push(dst);
subtreeIsTraversed = false;
break;
} else {
cycles.add(new ArrayList(path.subList(index, path.size())));
}
}
if (subtreeIsTraversed) {
stack.pop();
path.pop();
}
}
}
return cycles;
}
public static Digraph randomizeTree(
Digraph digraph, int maxChildren, int maxLevels, Random randomizer) {
int vertexIndex = 1;
Object root = new Integer(vertexIndex);
List level = Collections.singletonList(root);
digraph.addVertex(root);
for (int i = 1; i < maxLevels; i++) {
List childLevel = new ArrayList(level.size() * maxChildren);
for (Iterator j = level.iterator(); j.hasNext(); ) {
Object parent = j.next();
int childCount = randomizer.nextInt(maxChildren + 1);
for (int k = 0; k < childCount; k++) {
Object child = new Integer(++vertexIndex);
digraph.addVertex(child);
digraph.putArc(parent, child, Boolean.TRUE);
childLevel.add(child);
}
}
if (childLevel.isEmpty()) break;
level = childLevel;
}
return digraph;
}