sl@0: //
sl@0: //=======================================================================
sl@0: // Copyright 1997-2001 University of Notre Dame.
sl@0: // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
sl@0: //
sl@0: // Distributed under the Boost Software License, Version 1.0. (See
sl@0: // accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: //=======================================================================
sl@0: //
sl@0: #ifndef BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
sl@0: #define BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
sl@0: 
sl@0: #include <boost/config.hpp>
sl@0: #include <boost/graph/depth_first_search.hpp>
sl@0: #include <boost/graph/properties.hpp>
sl@0: #include <boost/graph/graph_concepts.hpp>
sl@0: 
sl@0: #include <boost/static_assert.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0:   namespace detail {
sl@0: 
sl@0:     // This visitor is used both in the connected_components algorithm
sl@0:     // and in the kosaraju strong components algorithm during the
sl@0:     // second DFS traversal.
sl@0:     template <class ComponentsMap>
sl@0:     class components_recorder : public dfs_visitor<>
sl@0:     {
sl@0:       typedef typename property_traits<ComponentsMap>::value_type comp_type;
sl@0:     public:
sl@0:       components_recorder(ComponentsMap c, 
sl@0:                           comp_type& c_count)
sl@0:         : m_component(c), m_count(c_count) {}
sl@0: 
sl@0:       template <class Vertex, class Graph>
sl@0:       void start_vertex(Vertex, Graph&) {
sl@0:         if (m_count == (std::numeric_limits<comp_type>::max)())
sl@0:           m_count = 0; // start counting components at zero
sl@0:         else
sl@0:           ++m_count;
sl@0:       }
sl@0:       template <class Vertex, class Graph>
sl@0:       void discover_vertex(Vertex u, Graph&) {
sl@0:         put(m_component, u, m_count);
sl@0:       }
sl@0:     protected:
sl@0:       ComponentsMap m_component;
sl@0:       comp_type& m_count;
sl@0:     };
sl@0: 
sl@0:   } // namespace detail
sl@0: 
sl@0:   // This function computes the connected components of an undirected
sl@0:   // graph using a single application of depth first search.
sl@0: 
sl@0:   template <class Graph, class ComponentMap, class P, class T, class R>
sl@0:   inline typename property_traits<ComponentMap>::value_type
sl@0:   connected_components(const Graph& g, ComponentMap c, 
sl@0:                        const bgl_named_params<P, T, R>& params)
sl@0:   {
sl@0:     if (num_vertices(g) == 0) return 0;
sl@0: 
sl@0:     typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
sl@0:     function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
sl@0:     typedef typename boost::graph_traits<Graph>::directed_category directed;
sl@0:     BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
sl@0: 
sl@0:     typedef typename property_traits<ComponentMap>::value_type comp_type;
sl@0:     // c_count initialized to "nil" (with nil represented by (max)())
sl@0:     comp_type c_count((std::numeric_limits<comp_type>::max)());
sl@0:     detail::components_recorder<ComponentMap> vis(c, c_count);
sl@0:     depth_first_search(g, params.visitor(vis));
sl@0:     return c_count + 1;
sl@0:   }
sl@0: 
sl@0:   template <class Graph, class ComponentMap>
sl@0:   inline typename property_traits<ComponentMap>::value_type
sl@0:   connected_components(const Graph& g, ComponentMap c)
sl@0:   {
sl@0:     if (num_vertices(g) == 0) return 0;
sl@0: 
sl@0:     typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
sl@0:     function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
sl@0:     typedef typename boost::graph_traits<Graph>::directed_category directed;
sl@0:     BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
sl@0: 
sl@0:     typedef typename property_traits<ComponentMap>::value_type comp_type;
sl@0:     // c_count initialized to "nil" (with nil represented by (max)())
sl@0:     comp_type c_count((std::numeric_limits<comp_type>::max)());
sl@0:     detail::components_recorder<ComponentMap> vis(c, c_count);
sl@0:     depth_first_search(g, visitor(vis));
sl@0:     return c_count + 1;
sl@0:   }
sl@0: 
sl@0:   
sl@0: } // namespace boost
sl@0: 
sl@0: 
sl@0: #endif // BOOST_GRAPH_CONNECTED_COMPONENTS_HPP