Boost C++ Libraries

libs/graph/example/bfs-example2.cpp

//=======================================================================
// Copyright 2001 Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee,
//
// 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)
//=======================================================================
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/breadth_first_search.hpp>
#include <boost/pending/indirect_cmp.hpp>
#include <boost/range/irange.hpp>
#include <boost/property_map/property_map.hpp>

#include <iostream>

using namespace boost;
template < typename TimeMap >
class bfs_time_visitor : public default_bfs_visitor
{
    typedef typename property_traits< TimeMap >::value_type T;

public:
    bfs_time_visitor(TimeMap tmap, T& t) : m_timemap(tmap), m_time(t) {}
    template < typename Vertex, typename Graph >
    void discover_vertex(Vertex u, const Graph& g) const
    {
        put(m_timemap, u, m_time++);
    }
    TimeMap m_timemap;
    T& m_time;
};

struct VertexProps
{
    boost::default_color_type color;
    std::size_t discover_time;
    unsigned int index;
};

int main()
{
    using namespace boost;
    // Select the graph type we wish to use
    typedef adjacency_list< listS, listS, undirectedS, VertexProps > graph_t;
    // Set up the vertex IDs and names
    enum
    {
        r,
        s,
        t,
        u,
        v,
        w,
        x,
        y,
        N
    };
    const char* name = "rstuvwxy";
    // Specify the edges in the graph
    typedef std::pair< int, int > E;
    E edge_array[] = { E(r, s), E(r, v), E(s, w), E(w, r), E(w, t), E(w, x),
        E(x, t), E(t, u), E(x, y), E(u, y) };
    // Create the graph object
    const int n_edges = sizeof(edge_array) / sizeof(E);
#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
    // VC++ has trouble with the edge iterator constructor
    graph_t g;
    std::vector< graph_traits< graph_t >::vertex_descriptor > verts;
    for (std::size_t i = 0; i < N; ++i)
        verts.push_back(add_vertex(g));
    for (std::size_t j = 0; j < n_edges; ++j)
        add_edge(verts[edge_array[j].first], verts[edge_array[j].second], g);
#else
    typedef graph_traits< graph_t >::vertices_size_type v_size_t;
    graph_t g(edge_array, edge_array + n_edges, v_size_t(N));
#endif

    // Typedefs
    typedef graph_traits< graph_t >::vertices_size_type Size;

    Size time = 0;
    typedef property_map< graph_t, std::size_t VertexProps::* >::type
        dtime_map_t;
    dtime_map_t dtime_map = get(&VertexProps::discover_time, g);
    bfs_time_visitor< dtime_map_t > vis(dtime_map, time);
    breadth_first_search(
        g, vertex(s, g), color_map(get(&VertexProps::color, g)).visitor(vis));

    // a vector to hold the discover time property for each vertex
    std::vector< Size > dtime(num_vertices(g));
    typedef iterator_property_map< std::vector< Size >::iterator,
        property_map< graph_t, unsigned int VertexProps::* >::type >
        dtime_pm_type;
    graph_traits< graph_t >::vertex_iterator vi, vi_end;
    std::size_t c = 0;
    for (boost::tie(vi, vi_end) = vertices(g); vi != vi_end; ++vi, ++c)
    {
        dtime[c] = dtime_map[*vi];
        put(&VertexProps::index, g, *vi, c);
    }
    dtime_pm_type dtime_pm(dtime.begin(), get(&VertexProps::index, g));

    // Use std::sort to order the vertices by their discover time
    std::vector< graph_traits< graph_t >::vertices_size_type > discover_order(
        N);
    integer_range< int > range(0, N);
    std::copy(range.begin(), range.end(), discover_order.begin());
    std::sort(discover_order.begin(), discover_order.end(),
        make_indirect_cmp(std::less< Size >(),
            make_iterator_property_map(
                dtime.begin(), typed_identity_property_map< std::size_t >())));

    std::cout << "order of discovery: ";
    for (int i = 0; i < N; ++i)
        std::cout << name[discover_order[i]] << " ";
    std::cout << std::endl;

    return EXIT_SUCCESS;
}