public static Map computeLevels(
Map vertexLevelMap, DigraphIteration digraph, Object root, boolean longest) {
if (vertexLevelMap == null) vertexLevelMap = new HashMap();
MutableInteger rootLevel = (MutableInteger) vertexLevelMap.get(root);
if (rootLevel == null) {
rootLevel = new MutableInteger(0);
vertexLevelMap.put(root, rootLevel);
}
for (ArcIterator i = digraph.outgoingIterator(root); i.hasNext(); ) {
i.next();
Object child = i.getDestination();
int childLevelCandidate = rootLevel.intValue() + 1;
MutableInteger childLevel = (MutableInteger) vertexLevelMap.get(child);
if (childLevel == null) {
childLevel = new MutableInteger(childLevelCandidate);
vertexLevelMap.put(child, childLevel);
computeLevels(vertexLevelMap, digraph, child, longest);
} else if ((longest && childLevel.intValue() < childLevelCandidate)
|| (!longest && childLevel.intValue() > childLevelCandidate)) {
childLevel.setValue(childLevelCandidate);
computeLevels(vertexLevelMap, digraph, child, longest);
}
}
return vertexLevelMap;
}
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 Map shiftLevelsDown(Map vertexLevelMap, DigraphIteration digraph, Object root) {
int minChildLevel = Integer.MAX_VALUE;
for (ArcIterator i = digraph.outgoingIterator(root); i.hasNext(); ) {
i.next();
Object child = i.getDestination();
shiftLevelsDown(vertexLevelMap, digraph, child);
MutableInteger childLevel = (MutableInteger) vertexLevelMap.get(child);
minChildLevel =
(minChildLevel <= childLevel.intValue() ? minChildLevel : childLevel.intValue());
}
if (minChildLevel != Integer.MAX_VALUE) {
MutableInteger rootLevel = (MutableInteger) vertexLevelMap.get(root);
rootLevel.setValue(minChildLevel - 1);
}
return vertexLevelMap;
}