Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the master branch, built from commit 81d917eed7.

libs/graph/example/city_visitor.cpp

//
//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// 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 <vector>
#include <string>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/depth_first_search.hpp>
#include <boost/graph/breadth_first_search.hpp>
#include <boost/property_map/property_map.hpp>
#include <boost/graph/graph_utility.hpp> // for boost::make_list

/*
  Example of using a visitor with the depth first search
    and breadth first search algorithm

  Sacramento ---- Reno ---- Salt Lake City
     |
  San Francisco
     |
  San Jose ---- Fresno
     |
  Los Angeles ---- Las Vegas ---- Phoenix
     |
  San Diego


  The visitor has three main functions:

  discover_vertex(u,g) is invoked when the algorithm first arrives at the
    vertex u. This will happen in the depth first or breadth first
    order depending on which algorithm you use.

  examine_edge(e,g) is invoked when the algorithm first checks an edge to see
    whether it has already been there. Whether using BFS or DFS, all
    the edges of vertex u are examined immediately after the call to
    visit(u).

  finish_vertex(u,g) is called when after all the vertices reachable from vertex
    u have already been visited.

 */

using namespace std;
using namespace boost;

struct city_arrival : public base_visitor< city_arrival >
{
    city_arrival(string* n) : names(n) {}
    typedef on_discover_vertex event_filter;
    template < class Vertex, class Graph >
    inline void operator()(Vertex u, Graph&)
    {
        cout << endl
             << "arriving at " << names[u] << endl
             << "  neighboring cities are: ";
    }
    string* names;
};

struct neighbor_cities : public base_visitor< neighbor_cities >
{
    neighbor_cities(string* n) : names(n) {}
    typedef on_examine_edge event_filter;
    template < class Edge, class Graph >
    inline void operator()(Edge e, Graph& g)
    {
        cout << names[target(e, g)] << ", ";
    }
    string* names;
};

struct finish_city : public base_visitor< finish_city >
{
    finish_city(string* n) : names(n) {}
    typedef on_finish_vertex event_filter;
    template < class Vertex, class Graph >
    inline void operator()(Vertex u, Graph&)
    {
        cout << endl << "finished with " << names[u] << endl;
    }
    string* names;
};

int main(int, char*[])
{

    enum
    {
        SanJose,
        SanFran,
        LA,
        SanDiego,
        Fresno,
        LasVegas,
        Reno,
        Sacramento,
        SaltLake,
        Phoenix,
        N
    };

    string names[]
        = { "San Jose", "San Francisco", "Los Angeles", "San Diego", "Fresno",
              "Las Vegas", "Reno", "Sacramento", "Salt Lake City", "Phoenix" };

    typedef std::pair< int, int > E;
    E edge_array[]
        = { E(Sacramento, Reno), E(Sacramento, SanFran), E(Reno, SaltLake),
              E(SanFran, SanJose), E(SanJose, Fresno), E(SanJose, LA),
              E(LA, LasVegas), E(LA, SanDiego), E(LasVegas, Phoenix) };

    /* Create the graph type we want. */
    typedef adjacency_list< vecS, vecS, undirectedS > Graph;
#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
    // VC++ has trouble with the edge iterator constructor
    Graph G(N);
    for (std::size_t j = 0; j < sizeof(edge_array) / sizeof(E); ++j)
        add_edge(edge_array[j].first, edge_array[j].second, G);
#else
    Graph G(edge_array, edge_array + sizeof(edge_array) / sizeof(E), N);
#endif

    cout << "*** Depth First ***" << endl;
    depth_first_search(G,
        visitor(make_dfs_visitor(boost::make_list(
            city_arrival(names), neighbor_cities(names), finish_city(names)))));
    cout << endl;

    /* Get the source vertex */
    boost::graph_traits< Graph >::vertex_descriptor s = vertex(SanJose, G);

    cout << "*** Breadth First ***" << endl;
    breadth_first_search(G, s,
        visitor(make_bfs_visitor(boost::make_list(
            city_arrival(names), neighbor_cities(names), finish_city(names)))));

    return 0;
}