提升图形库:防止 DFS 访问未连接的节点

我有一个双向图。某些顶点未连接。我使用 boost：:d epth_first_search 来遍历顶点。我还提供起始源节点。我看到未连接的顶点也在连接的节点完成后进行处理。如何防止访问此类节点？事实上，如何告诉 DFS 只访问可从源节点访问的节点，而不访问其他任何节点？

我有以下代码：

/// Define vertex properties.
struct NodeProperty
{
    unsigned     id;              /// Id.
    unsigned     kind;            /// Kind.
    unsigned     depth;           /// Depth.
    unsigned     layer_color;     /// Layer color.
    unsigned     signal_color;    /// Signal color.
    unsigned     sch_color;       /// Sch color.
    CBoundingBox bounds;          /// Bounds of polygon.
    NodeProperty()
        : id(0), kind(0), depth(0), layer_color(0), signal_color(0), sch_color(0), bounds(0,0,0,0)
    {
        ;
    }
};
/// Define net topology graph.
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, NodeProperty> Graph;
class receiver_visitor : public boost::default_dfs_visitor
{
    public:
        receiver_visitor(std::vector<Vertex>& r)
            : res(r)
        {
            ;
        }
        void discover_vertex(Vertex v, Graph const& g) const
        {
            std::cout << "Visit: " << v << std::endl;
            if (g[v].sch_color) {
                res.push_back(g[v].sch_color);
            }
        }
        std::vector<Vertex>& res;
 };
 std::vector<std::size_t>
 NetTopology::getReceivers(std::size_t src) const
 {
     std::vector<Vertex> r;
     receiver_visitor vis(r);
     boost::depth_first_search(data_->g, boost::visitor(vis).root_vertex(src));
     return r;
}