public static boolean isAcyclic(Digraph digraph) { int order = digraph.order(); if (order == 0) return true; Set spanned = new HashSet(order); DepthFirstStampSearch dfs = new DepthFirstStampSearch(digraph, digraph.vertexIterator().next()); for (Iterator i = digraph.vertexIterator(); i.hasNext(); ) { Object dfsRoot = i.next(); if (spanned.contains(dfsRoot)) continue; dfs.reset(dfsRoot); Map dfsOrders = dfs.traverse(new HashMap(digraph.order())); for (Iterator j = dfsOrders.entrySet().iterator(); j.hasNext(); ) { Map.Entry entry = (Map.Entry) j.next(); Object origin = entry.getKey(); DepthFirstStampSearch.OrderPair orgOrders = (DepthFirstStampSearch.OrderPair) entry.getValue(); spanned.add(origin); for (ArcIterator k = digraph.outgoingIterator(origin); k.hasNext(); ) { k.next(); Object dst = k.getDestination(); DepthFirstStampSearch.OrderPair dstOrders = (DepthFirstStampSearch.OrderPair) dfsOrders.get(dst); if (dstOrders.getPostOrder() > orgOrders.getPostOrder()) return false; } } if (dfsOrders.size() == order) break; } return true; }
public static Map computeLevels(Map vertexLevelMap, Digraph digraph, boolean longest) { if (vertexLevelMap == null) vertexLevelMap = new HashMap(digraph.order()); for (Iterator i = digraph.vertexIterator(); i.hasNext(); ) { Object rootCandidate = i.next(); if (digraph.incomingSize(rootCandidate) == 0) computeLevels(vertexLevelMap, digraph, rootCandidate, longest); } return vertexLevelMap; }
public static boolean isStronglyConnected(Digraph digraph) { return isStronglyConnected(digraph, digraph.vertexIterator().next(), digraph.order()); }