Example #1
0
 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;
 }
Example #2
0
  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;
  }
Example #3
0
 public static boolean isStronglyConnected(Digraph digraph) {
   return isStronglyConnected(digraph, digraph.vertexIterator().next(), digraph.order());
 }