Ejemplo n.º 1
0
 private boolean findCycleWithBfs(Vertex current, Vertex to, Set<Vertex> ignoreSet) {
   Set<Vertex> neighbours = data.get(current);
   for (Vertex neighbour : neighbours) {
     if (ignoreSet.contains(neighbour)) {
       continue;
     }
     if (neighbour.equals(to)) {
       return true;
     }
     Set<Vertex> newIgnoreSet = new HashSet<>(ignoreSet);
     newIgnoreSet.add(neighbour);
     boolean foundCycle = findCycleWithBfs(neighbour, to, newIgnoreSet);
     if (foundCycle) {
       return true;
     }
   }
   return false;
 }
Ejemplo n.º 2
0
    /**
     * Essentially uses bfs to find if there exists a cycle between two vertices of the new edge.
     *
     * @param edge edge for which we are looking a cycle
     * @return true if there exists a cycle. false otherwise
     */
    private boolean hasCycle(Edge edge) {
      // if any of two vertices of the edge is not already in the disjoint set then there can't be a
      // cycle either
      if (!data.containsKey(edge.getFrom()) || !data.containsKey(edge.getTo())) {
        return false;
      }

      Set<Vertex> fromNeighbours = data.get(edge.getFrom());
      for (Vertex neighbour : fromNeighbours) {
        boolean foundCycle = false;
        if (!neighbour.equals(edge.getTo())) {
          Set<Vertex> set = new HashSet<>();
          set.add(neighbour);
          foundCycle = findCycleWithBfs(neighbour, edge.getTo(), set);
        }
        if (foundCycle) {
          return true;
        }
      }

      return false;
    }