boost/graph/connected_components.hpp
//
//=======================================================================
// Copyright 1997-2001 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// This file is part of the Boost Graph Library
//
// You should have received a copy of the License Agreement for the
// Boost Graph Library along with the software; see the file LICENSE.
// If not, contact Office of Research, University of Notre Dame, Notre
// Dame, IN 46556.
//
// Permission to modify the code and to distribute modified code is
// granted, provided the text of this NOTICE is retained, a notice that
// the code was modified is included with the above COPYRIGHT NOTICE and
// with the COPYRIGHT NOTICE in the LICENSE file, and that the LICENSE
// file is distributed with the modified code.
//
// LICENSOR MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.
// By way of example, but not limitation, Licensor MAKES NO
// REPRESENTATIONS OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY
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// OR OTHER RIGHTS.
//=======================================================================
//
#ifndef BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
#define BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
#include <boost/config.hpp>
#include <boost/graph/depth_first_search.hpp>
#include <boost/graph/properties.hpp>
#include <boost/graph/graph_concepts.hpp>
#include <boost/static_assert.hpp>
namespace boost {
namespace detail {
// This visitor is used both in the connected_components algorithm
// and in the kosaraju strong components algorithm during the
// second DFS traversal.
template <class ComponentsMap>
class components_recorder : public dfs_visitor<>
{
typedef typename property_traits<ComponentsMap>::value_type comp_type;
public:
components_recorder(ComponentsMap c,
comp_type& c_count)
: m_component(c), m_count(c_count) {}
template <class Vertex, class Graph>
void start_vertex(Vertex, Graph&) {
if (m_count == (std::numeric_limits<comp_type>::max)())
m_count = 0; // start counting components at zero
else
++m_count;
}
template <class Vertex, class Graph>
void discover_vertex(Vertex u, Graph&) {
put(m_component, u, m_count);
}
protected:
ComponentsMap m_component;
comp_type& m_count;
};
} // namespace detail
// This function computes the connected components of an undirected
// graph using a single application of depth first search.
template <class Graph, class ComponentMap, class P, class T, class R>
inline typename property_traits<ComponentMap>::value_type
connected_components(const Graph& g, ComponentMap c,
const bgl_named_params<P, T, R>& params)
{
typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
typedef typename boost::graph_traits<Graph>::directed_category directed;
BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
typedef typename property_traits<ComponentMap>::value_type comp_type;
// c_count initialized to "nil" (with nil represented by max())
comp_type c_count((std::numeric_limits<comp_type>::max)());
detail::components_recorder<ComponentMap> vis(c, c_count);
depth_first_search(g, params.visitor(vis));
return c_count + 1;
}
template <class Graph, class ComponentMap>
inline typename property_traits<ComponentMap>::value_type
connected_components(const Graph& g, ComponentMap c)
{
typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
function_requires< WritablePropertyMapConcept<ComponentMap, Vertex> >();
typedef typename boost::graph_traits<Graph>::directed_category directed;
BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
typedef typename property_traits<ComponentMap>::value_type comp_type;
// c_count initialized to "nil" (with nil represented by max())
comp_type c_count((std::numeric_limits<comp_type>::max)());
detail::components_recorder<ComponentMap> vis(c, c_count);
depth_first_search(g, visitor(vis));
return c_count + 1;
}
} // namespace boost
#endif // BOOST_GRAPH_CONNECTED_COMPONENTS_HPP