void dfsR(Graph g, Vertex v) {
   visited[v] = order++;
   Vertex w;
   for (w = 0; w < g->nV; w++) {
      if (!g->edges[v][w]) continue;
      if (visited[w] == -1) dfsR(g, w);
}  }

0->1,4,5  1->0,2  2->1,3,4  3->2,4,5  4->0,2,3,5  5->0,3,4

            order  visited
init        0      [X,X,X,X,X,X]
dfsR(g,0)   0      [0,X,X,X,X,X]