On Tue, 15 Dec 2009, Suresh Kumar wrote:
Hi, my idea is to get the finishing order of vertices in dfs by pushing the vertices in a vector and return it later through a function return value from my visitor class object. //code snippet int main() { my_visitor vis; depth_first_search(g, visitor(vis)); cout << "size of fin vector = " << vis.finishingOrder.size() << endl; //i get zero here!!! }
class my_visitor: public default_dfs_visitor { public: my_visitor(){} void finish_vertex(Vertex u, const Graph & g){finishingOrder.push_back(u);}; vector<Vertex> getFinishingOrder(void){return finishingOrder;} private: vector<Vertex> finishingOrder; };
My problem: size of the finishingOrder vector is zero outside the my_visitor::finish_vertex method. I checked its size inside the my_visitor::finish_vertex method and its value is increasing every time a vertex is finished.
Does I miss something in the understanding of the visitor concept?
Someone asked basically the same question in the thread "[Boost-users] boost graph library, default_dfs_visitor, dfs". The visitor is copied by the algorithm, so you will need to have the finishingOrder vector be a reference to an externally declared vector. Have your main program declare such a vector and have the visitor contain a reference member that points to it; then the vector will be available even after the algorithm finishes. -- Jeremiah Willcock