63e88f80
 Hu Chunming
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// Copyright (C) 2006 The Trustees of Indiana University.
// Use, modification and distribution is subject to 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)
// Authors: Douglas Gregor
// Andrew Lumsdaine
#ifndef BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
#define BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/two_bit_color_map.hpp>
#include <boost/graph/iteration_macros.hpp>
#include <boost/pending/queue.hpp>
namespace boost
{
namespace graph
{
template < typename Graph, typename ColorMap >
bool st_connected(const Graph& g,
typename graph_traits< Graph >::vertex_descriptor s,
typename graph_traits< Graph >::vertex_descriptor t, ColorMap color)
{
typedef typename property_traits< ColorMap >::value_type Color;
typedef color_traits< Color > ColorTraits;
typedef typename graph_traits< Graph >::vertex_descriptor Vertex;
// Set all vertices to white (unvisited)
BGL_FORALL_VERTICES_T(v, g, Graph)
put(color, v, ColorTraits::white());
// Vertices found from the source are grey
put(color, s, ColorTraits::gray());
// Vertices found from the target are greeen
put(color, t, ColorTraits::green());
queue< Vertex > Q;
Q.push(s);
Q.push(t);
while (!Q.empty())
{
Vertex u = Q.top();
Q.pop();
Color u_color = get(color, u);
BGL_FORALL_OUTEDGES_T(u, e, g, Graph)
{
Vertex v = target(e, g);
Color v_color = get(color, v);
if (v_color == ColorTraits::white())
{
// We have not seen "v" before; mark it with the same color
// as u
Color u_color = get(color, u);
put(color, v, u_color);
// Push it on the queue
Q.push(v);
}
else if (v_color != ColorTraits::black() && u_color != v_color)
{
// Colors have collided. We're done!
return true;
}
}
// u is done, so mark it black
put(color, u, ColorTraits::black());
}
return false;
}
template < typename Graph >
inline bool st_connected(const Graph& g,
typename graph_traits< Graph >::vertex_descriptor s,
typename graph_traits< Graph >::vertex_descriptor t)
{
return st_connected(g, s, t,
make_two_bit_color_map(num_vertices(g), get(vertex_index, g)));
}
}
} // end namespace boost::graph
#endif // BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
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