Code Fragment: ConnectTestDFS

template <typename Graph>
class ConnectivityTesterDFS : public DFS<Graph> {	// test connectivity
protected: 						// local types
  typedef typename Graph::Vertex Vertex;
private:
  int reached;						// how many verts reached
protected: 						// overriden functions
  virtual void startVisit(const Vertex& v)		// count visited vertex
    { reached++; }
public:
   ConnectivityTesterDFS(const Graph& g) 		// constructor
     : DFS<Graph>(g) { }
   bool run() {						// main entry point
    initialize();					// initialize DFS
    reached = 0;					// init vertex count
    if (!G.isEmpty()) {
      Vertex v = G.aVertex();				// select any vertex
      dfsTraversal(v);					// start DFS here
    }
    return (reached == G.numVertices());		// visit all => connected
  }
};