Boost C++ Libraries

libs/graph/example/dijkstra-example.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/config.hpp>
#include <iostream>
#include <fstream>

#include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/property_map/property_map.hpp>

using namespace boost;

int main(int, char*[])
{
    typedef adjacency_list< listS, vecS, directedS, no_property,
        property< edge_weight_t, int > >
        graph_t;
    typedef graph_traits< graph_t >::vertex_descriptor vertex_descriptor;
    typedef std::pair< int, int > Edge;

    const int num_nodes = 5;
    enum nodes
    {
        A,
        B,
        C,
        D,
        E
    };
    char name[] = "ABCDE";
    Edge edge_array[] = { Edge(A, C), Edge(B, B), Edge(B, D), Edge(B, E),
        Edge(C, B), Edge(C, D), Edge(D, E), Edge(E, A), Edge(E, B) };
    int weights[] = { 1, 2, 1, 2, 7, 3, 1, 1, 1 };
    int num_arcs = sizeof(edge_array) / sizeof(Edge);
    graph_t g(edge_array, edge_array + num_arcs, weights, num_nodes);
    property_map< graph_t, edge_weight_t >::type weightmap
        = get(edge_weight, g);
    std::vector< vertex_descriptor > p(num_vertices(g));
    std::vector< int > d(num_vertices(g));
    vertex_descriptor s = vertex(A, g);

    dijkstra_shortest_paths(g, s,
        predecessor_map(boost::make_iterator_property_map(
                            p.begin(), get(boost::vertex_index, g)))
            .distance_map(boost::make_iterator_property_map(
                d.begin(), get(boost::vertex_index, g))));

    std::cout << "distances and parents:" << std::endl;
    graph_traits< graph_t >::vertex_iterator vi, vend;
    for (boost::tie(vi, vend) = vertices(g); vi != vend; ++vi)
    {
        std::cout << "distance(" << name[*vi] << ") = " << d[*vi] << ", ";
        std::cout << "parent(" << name[*vi] << ") = " << name[p[*vi]]
                  << std::endl;
    }
    std::cout << std::endl;

    std::ofstream dot_file("figs/dijkstra-eg.dot");

    dot_file << "digraph D {\n"
             << "  rankdir=LR\n"
             << "  size=\"4,3\"\n"
             << "  ratio=\"fill\"\n"
             << "  edge[style=\"bold\"]\n"
             << "  node[shape=\"circle\"]\n";

    graph_traits< graph_t >::edge_iterator ei, ei_end;
    for (boost::tie(ei, ei_end) = edges(g); ei != ei_end; ++ei)
    {
        graph_traits< graph_t >::edge_descriptor e = *ei;
        graph_traits< graph_t >::vertex_descriptor u = source(e, g),
                                                   v = target(e, g);
        dot_file << name[u] << " -> " << name[v] << "[label=\""
                 << get(weightmap, e) << "\"";
        if (p[v] == u)
            dot_file << ", color=\"black\"";
        else
            dot_file << ", color=\"grey\"";
        dot_file << "]";
    }
    dot_file << "}";
    return EXIT_SUCCESS;
}