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//=======================================================================

// 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 <algorithm>

#include <vector>

#include <utility>

#include <iostream>

#include <boost/graph/graph_utility.hpp>

#include <boost/graph/visitors.hpp>

#include <boost/graph/adjacency_list.hpp>

#include <boost/graph/neighbor_bfs.hpp>

#include <boost/property_map/property_map.hpp>

This examples shows how to use the breadth_first_search() GGCL

algorithm, specifically the 3 argument variant of bfs that assumes

the graph has a color property (property) stored internally.

Two pre-defined visitors are used to record the distance of each

vertex from the source vertex, and also to record the parent of each

vertex. Any number of visitors can be layered and passed to a GGCL

algorithm.

The call to vertices(G) returns an STL-compatible container which

contains all of the vertices in the graph. In this example we use

the vertices container in the STL for_each() function.

Sample Output:

0 --> 2

1 --> 1 3 4

2 --> 1 3 4

3 --> 1 4

4 --> 0 1

distances: 1 2 1 2 0

parent[0] = 4

parent[1] = 2

parent[2] = 0

parent[3] = 2

parent[4] = 0

template < class ParentDecorator > struct print_parent

{

print_parent(const ParentDecorator& p_) : p(p_) {}

template < class Vertex > void operator()(const Vertex& v) const

{

std::cout << "parent[" << v << "] = " << p[v] << std::endl;

}

ParentDecorator p;

};

template < class NewGraph, class Tag >

struct graph_copier

: public boost::base_visitor< graph_copier< NewGraph, Tag > >

{

using event_filter = Tag;

graph_copier(NewGraph& graph) : new_g(graph) {}

template < class Edge, class Graph > void operator()(Edge e, Graph& g)

{

boost::add_edge(boost::source(e, g), boost::target(e, g), new_g);

}

private:

NewGraph& new_g;

};

template < class NewGraph, class Tag >

inline graph_copier< NewGraph, Tag > copy_graph(NewGraph& g, Tag)

{

return graph_copier< NewGraph, Tag >(g);

}

int main(int, char*[])

{

using Graph = boost::adjacency_list< boost::mapS, boost::vecS,

boost::bidirectionalS,

boost::property< boost::vertex_color_t, boost::default_color_type,

boost::property< boost::vertex_degree_t, int,

boost::property< boost::vertex_in_degree_t, int,

boost::property< boost::vertex_out_degree_t, int > > > > >;

Graph G(5);

boost::add_edge(0, 2, G);

boost::add_edge(1, 1, G);

boost::add_edge(1, 3, G);

boost::add_edge(1, 4, G);

boost::add_edge(2, 1, G);

boost::add_edge(2, 3, G);

boost::add_edge(2, 4, G);

boost::add_edge(3, 1, G);

boost::add_edge(3, 4, G);

boost::add_edge(4, 0, G);

boost::add_edge(4, 1, G);

using Vertex = Graph::vertex_descriptor;

// Array to store predecessor (parent) of each vertex. This will be

// used as a Decorator (actually, its iterator will be).

std::vector< Vertex > p(boost::num_vertices(G));

// VC++ version of std::vector has no ::pointer, so

// I use ::value_type* instead.

using Piter = std::vector< Vertex >::value_type*;

// Array to store distances from the source to each vertex . We use

// a built-in array here just for variety. This will also be used as

// a Decorator.

boost::graph_traits< Graph >::vertices_size_type d[5];

std::fill_n(d, 5, 0);

// The source vertex

auto s = *(boost::vertices(G).first);

p[s] = s;

boost::neighbor_breadth_first_search(G, s,

boost::visitor(boost::make_neighbor_bfs_visitor(

std::make_pair(boost::record_distances(d, boost::on_tree_edge()),

boost::record_predecessors(&p[0], boost::on_tree_edge())))));

boost::print_graph(G);

if (boost::num_vertices(G) < 11)

{

std::cout << "distances: ";

#ifdef BOOST_OLD_STREAM_ITERATORS

std::copy(d, d + 5, std::ostream_iterator< int, char >(std::cout, " "));

#else

std::copy(d, d + 5, std::ostream_iterator< int >(std::cout, " "));

#endif

std::cout << std::endl;

std::for_each(boost::vertices(G).first, boost::vertices(G).second,

print_parent< Piter >(&p[0]));

}

return 0;

}