class Graph {

    public Configuration configurationOf(int u) {

        Topology t = topologyOf(u);

        if (t == Topology.unknown())
            return t.configuration();

        // identity permutation
        int[] p = new int[order];
        for (int i = 0; i < order; i++)
            p[i] = i;

        return t.orderBy(p).configuration();
    }

      Graph(int expSize);
      Graph(Graph org);

}