williamr@2: //
williamr@2: //=======================================================================
williamr@2: // Copyright 1997-2001 University of Notre Dame.
williamr@2: // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: //=======================================================================
williamr@2: //
williamr@2: #ifndef BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
williamr@2: #define BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
williamr@2: 
williamr@2: #include <boost/config.hpp>
williamr@2: #include <boost/graph/depth_first_search.hpp>
williamr@2: #include <boost/graph/properties.hpp>
williamr@2: #include <boost/graph/graph_concepts.hpp>
williamr@2: 
williamr@2: #include <boost/static_assert.hpp>
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2:   namespace detail {
williamr@2: 
williamr@2:     // This visitor is used both in the connected_components algorithm
williamr@2:     // and in the kosaraju strong components algorithm during the
williamr@2:     // second DFS traversal.
williamr@2:     template <class ComponentsMap>
williamr@2:     class components_recorder : public dfs_visitor<>
williamr@2:     {
williamr@2:       typedef typename property_traits<ComponentsMap>::value_type comp_type;
williamr@2:     public:
williamr@2:       components_recorder(ComponentsMap c, 
williamr@2:                           comp_type& c_count)
williamr@2:         : m_component(c), m_count(c_count) {}
williamr@2: 
williamr@2:       template <class Vertex, class Graph>
williamr@2:       void start_vertex(Vertex, Graph&) {
williamr@2:         if (m_count == (std::numeric_limits<comp_type>::max)())
williamr@2:           m_count = 0; // start counting components at zero
williamr@2:         else
williamr@2:           ++m_count;
williamr@2:       }
williamr@2:       template <class Vertex, class Graph>
williamr@2:       void discover_vertex(Vertex u, Graph&) {
williamr@2:         put(m_component, u, m_count);
williamr@2:       }
williamr@2:     protected:
williamr@2:       ComponentsMap m_component;
williamr@2:       comp_type& m_count;
williamr@2:     };
williamr@2: 
williamr@2:   } // namespace detail
williamr@2: 
williamr@2:   // This function computes the connected components of an undirected
williamr@2:   // graph using a single application of depth first search.
williamr@2: 
williamr@2:   template <class Graph, class ComponentMap, class P, class T, class R>
williamr@2:   inline typename property_traits<ComponentMap>::value_type
williamr@2:   connected_components(const Graph& g, ComponentMap c, 
williamr@2:                        const bgl_named_params<P, T, R>& params)
williamr@2:   {
williamr@2:     if (num_vertices(g) == 0) return 0;
williamr@2: 
williamr@2:     typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
williamr@2:     function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
williamr@2:     typedef typename boost::graph_traits<Graph>::directed_category directed;
williamr@2:     BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
williamr@2: 
williamr@2:     typedef typename property_traits<ComponentMap>::value_type comp_type;
williamr@2:     // c_count initialized to "nil" (with nil represented by (max)())
williamr@2:     comp_type c_count((std::numeric_limits<comp_type>::max)());
williamr@2:     detail::components_recorder<ComponentMap> vis(c, c_count);
williamr@2:     depth_first_search(g, params.visitor(vis));
williamr@2:     return c_count + 1;
williamr@2:   }
williamr@2: 
williamr@2:   template <class Graph, class ComponentMap>
williamr@2:   inline typename property_traits<ComponentMap>::value_type
williamr@2:   connected_components(const Graph& g, ComponentMap c)
williamr@2:   {
williamr@2:     if (num_vertices(g) == 0) return 0;
williamr@2: 
williamr@2:     typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
williamr@2:     function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
williamr@2:     typedef typename boost::graph_traits<Graph>::directed_category directed;
williamr@2:     BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
williamr@2: 
williamr@2:     typedef typename property_traits<ComponentMap>::value_type comp_type;
williamr@2:     // c_count initialized to "nil" (with nil represented by (max)())
williamr@2:     comp_type c_count((std::numeric_limits<comp_type>::max)());
williamr@2:     detail::components_recorder<ComponentMap> vis(c, c_count);
williamr@2:     depth_first_search(g, visitor(vis));
williamr@2:     return c_count + 1;
williamr@2:   }
williamr@2: 
williamr@2:   
williamr@2: } // namespace boost
williamr@2: 
williamr@2: 
williamr@2: #endif // BOOST_GRAPH_CONNECTED_COMPONENTS_HPP