// does the id[] array contain the strongly connected components? private boolean check(Digraph G) { TransitiveClosure tc = new TransitiveClosure(G); for (int v = 0; v < G.V(); v++) { for (int w = 0; w < G.V(); w++) { if (stronglyConnected(v, w) != (tc.reachable(v, w) && tc.reachable(w, v))) return false; } } return true; }