Re: [Boost-users] Cycle detection in a directed graph with adjacency_matrix

Subject: Re: [Boost-users] Cycle detection in a directed graph with adjacency_matrix
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-04-12 22:40:13

On Tue, 12 Apr 2011, albert kao wrote:

> After adding "boost::" before "graph_traits", the compile errors are:
> adjacency_matrix_is_cyclic.cpp:9: error: expected class-name before ‘{’ token
> adjacency_matrix_is_cyclic.cpp: In function ‘bool has_cycle(const Graph&)’:
> adjacency_matrix_is_cyclic.cpp:26: error: ‘generic_dfs_v1’ was not declared in this scope
> 
> adjacency_matrix_is_cyclic.cpp:
> #include <iostream>
> #include <boost/graph/graph_utility.hpp>
> #include <boost/graph/adjacency_matrix.hpp>
> 
> typedef boost::adjacency_matrix<boost::directedS> Graph;
> typedef boost::graph_traits<Graph>::edge_descriptor edge_t;
>   
> struct cycle_detector : public dfs_visitor_default
> {
>   cycle_detector(bool & cycle): has_cycle(cycle)
>   {
>   }
>   void
>   back_edge(edge_t, const Graph &)
>   {
>     has_cycle = true;
>   }
>   bool & has_cycle;
> };
> 
> bool
> has_cycle(const Graph & g)
> {
>   bool has_cycle = false;
>   cycle_detector vis(has_cycle);
>   generic_dfs_v1(g, vis);
>   return has_cycle;
> }
> 
> enum { A, B, C, D, E, F, N };
> const char* name = "ABCDEF";
> 
> int main(int argc, char *argv[])
> {
>   Graph g(N);
>   add_edge(B, C, g);
>   add_edge(B, F, g);
>   add_edge(C, A, g);
>   add_edge(C, C, g);
>   add_edge(D, E, g);
>   add_edge(E, D, g);
>   add_edge(F, A, g);
> 
>   std::cout << "vertex set: ";
>   boost::print_vertices(g, name);
>   std::cout << std::endl;
> 
>   std::cout << "edge set: ";
>   boost::print_edges(g, name);
>   std::cout << std::endl;
> 
>   std::cout << "out-edges: " << std::endl;
>   boost::print_graph(g, name);
>   std::cout << std::endl;
> 
>   std::cout << "has_cycle(g) " << has_cycle(g) << std::endl;
> 
>   return 0;
> }

You also need boost:: before dfs_visitor_default.  You should also use 
boost::depth_first_search instead of generic_dfs_v1 (which is internal).

-- Jeremiah Willcock