BFS in Boost graph library

[rboorgapally]

Hi everyone,
I am trying to run BFS on a graph that is created with input from a file. I am facing problems with the output though the code is compiling:

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/depth_first_search.hpp>
#include <fstream>
#include <utility>
#include <boost/graph/breadth_first_search.hpp>
#include <algorithm>
 
namespace std {
 
  using namespace boost;
 
  template <typename T>
  std::istream& operator>> (std::istream& in, std::pair<T,T>& p) {
     in >> p.first >> p.second;
     return in;
  }
 
  class graph_out : public default_bfs_visitor {
    public:
    graph_out() : ecounter(0) {}
 
    template <typename Edge, typename Graph>
    void tree_edge(Edge u, const Graph&) {
       std::cout << "discovered an edge" << endl;
       std::cout << ecounter++ << u;
    }
 
    private:
    int ecounter;
 
  };
 
}
 
 
 
int main(){
  using namespace std;
  using namespace boost;
  typedef adjacency_list <listS, vecS, directedS> file_dep_graph;
 
  std::ifstream file_in("directed_graph.dat");
  typedef graph_traits<file_dep_graph>::vertices_size_type size_type;
  size_type n_vertices;
 
  if(file_in >> n_vertices){
    std::cout << n_vertices << endl; // read in number of vertices
  }
 
  istream_iterator<std::pair<size_type, size_type> >
  input_begin(file_in), input_end;
 
  file_dep_graph g(input_begin, input_end, n_vertices);
 
  graph_out vis;
  graph_traits<file_dep_graph>::vertex_descriptor a = *vertices(g).first;
  breadth_first_search(g,a,visitor(vis));
 
}

The directed_graph. dat file is:

14
(1,2)
(2,3)
(3,4)
(3,5)
(4,6)
(6,7)
(7,8)
(7,9)
(7,10)
(8,11)
(9,12)
(12,13)
(13,14)

Please dont suggest me any alternatives, such as without using a file etc as I need to do it this way only.

[rboorgapally]

Hi everyone,
I found the answer :)
I entered the values in the directed_graph. dat file wrongly.
We shouldn't enter the values in pairs.
We should do so in inegers.