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boost/graph/make_connected.hpp

//=======================================================================
// Copyright 2007 Aaron Windsor
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================
#ifndef __MAKE_CONNECTED_HPP__
#define __MAKE_CONNECTED_HPP__

#include <boost/config.hpp>
#include <boost/utility.hpp> //for next
#include <boost/tuple/tuple.hpp>   //for tie
#include <boost/graph/connected_components.hpp>
#include <boost/property_map/property_map.hpp>
#include <vector>

#include <boost/graph/planar_detail/add_edge_visitors.hpp>
#include <boost/graph/planar_detail/bucket_sort.hpp>


namespace boost
{


  template <typename Graph,
            typename VertexIndexMap,
            typename AddEdgeVisitor
            >
  void make_connected(Graph& g, VertexIndexMap vm, AddEdgeVisitor& vis)
  {
    typedef typename graph_traits<Graph>::vertex_iterator vertex_iterator_t;
    typedef typename graph_traits<Graph>::vertex_descriptor vertex_t;
    typedef typename graph_traits<Graph>::vertices_size_type v_size_t;
    typedef iterator_property_map< typename std::vector<v_size_t>::iterator,
                                   VertexIndexMap
                                  > vertex_to_v_size_map_t;

    std::vector<v_size_t> component_vector(num_vertices(g));
    vertex_to_v_size_map_t component(component_vector.begin(), vm);
    std::vector<vertex_t> vertices_by_component(num_vertices(g));

    v_size_t num_components = connected_components(g, component);

    if (num_components < 2)
      return;

    vertex_iterator_t vi, vi_end;
    boost::tie(vi,vi_end) = vertices(g);
    std::copy(vi, vi_end, vertices_by_component.begin());

    bucket_sort(vertices_by_component.begin(),
                vertices_by_component.end(),
                component,
                num_components
                );

    typedef typename std::vector<vertex_t>::iterator vec_of_vertices_itr_t;

    vec_of_vertices_itr_t ci_end = vertices_by_component.end();
    vec_of_vertices_itr_t ci_prev = vertices_by_component.begin();
    if (ci_prev == ci_end)
      return;

    for(vec_of_vertices_itr_t ci = boost::next(ci_prev); 
        ci != ci_end;  ci_prev = ci, ++ci
        )
      {
        if (component[*ci_prev] != component[*ci])
          vis.visit_vertex_pair(*ci_prev, *ci, g);
      }

  }




  template <typename Graph, typename VertexIndexMap>
  inline void make_connected(Graph& g, VertexIndexMap vm)
  {
    default_add_edge_visitor vis;
    make_connected(g, vm, vis);
  }




  template <typename Graph>
  inline void make_connected(Graph& g)
  {
    make_connected(g, get(vertex_index,g));
  }




} // namespace boost 

#endif //__MAKE_CONNECTED_HPP__