\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - CGAL and the Boost Graph Library

All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Groups Pages
BGL_triangulation_2/dijkstra.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Triangulation_2.h>
#include <CGAL/boost/graph/graph_traits_Triangulation_2.h>
#include <CGAL/boost/graph/dijkstra_shortest_paths.h>
#include <boost/graph/filtered_graph.hpp>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_2 Point;
typedef CGAL::Triangulation_2<K> Triangulation;
// As we want to run Dijskra's shortest path algorithm we only
// consider finite vertices and edges.
template <typename T>
struct Is_finite {
const T* t_;
Is_finite()
: t_(NULL)
{}
Is_finite(const T& t)
: t_(&t)
{ }
template <typename VertexOrEdge>
bool operator()(const VertexOrEdge& voe) const {
return ! t_->is_infinite(voe);
}
};
typedef Is_finite<Triangulation> Filter;
typedef boost::filtered_graph<Triangulation,Filter,Filter> Finite_triangulation;
typedef boost::graph_traits<Finite_triangulation>::vertex_descriptor vertex_descriptor;
typedef boost::graph_traits<Finite_triangulation>::vertex_iterator vertex_iterator;
typedef std::map<vertex_descriptor,int> VertexIndexMap;
VertexIndexMap vertex_id_map;
typedef boost::associative_property_map<VertexIndexMap> VertexIdPropertyMap;
VertexIdPropertyMap vertex_index_pmap(vertex_id_map);
int
main(int,char*[])
{
Triangulation t;
Filter is_finite(t);
Finite_triangulation ft(t, is_finite, is_finite);
t.insert(Point(0,0));
t.insert(Point(1,0));
t.insert(Point(0.2,0.2));
t.insert(Point(0,1));
t.insert(Point(0,2));
vertex_iterator vit, ve;
// Associate indices to the vertices
int index = 0;
// boost::tie assigns the first and second element of the std::pair
// returned by boost::vertices to the variables vit and ve
for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
vertex_descriptor vd = *vit;
vertex_id_map[vd]= index++;
}
// Dijkstra's shortest path needs property maps for the predecessor and distance
// We first declare a vector
std::vector<vertex_descriptor> predecessor(boost::num_vertices(ft));
// and then turn it into a property map
boost::iterator_property_map<std::vector<vertex_descriptor>::iterator,
VertexIdPropertyMap>
predecessor_pmap(predecessor.begin(), vertex_index_pmap);
std::vector<double> distance(boost::num_vertices(ft));
boost::iterator_property_map<std::vector<double>::iterator,
VertexIdPropertyMap>
distance_pmap(distance.begin(), vertex_index_pmap);
// start at an arbitrary vertex
vertex_descriptor source = *boost::vertices(ft).first;
std::cout << "\nStart dijkstra_shortest_paths at " << source->point() <<"\n";
boost::dijkstra_shortest_paths(ft, source,
distance_map(distance_pmap)
.predecessor_map(predecessor_pmap)
.vertex_index_map(vertex_index_pmap));
for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
vertex_descriptor vd = *vit;
std::cout << vd->point() << " [" << vertex_id_map[vd] << "] ";
std::cout << " has distance = " << boost::get(distance_pmap,vd)
<< " and predecessor ";
vd = boost::get(predecessor_pmap,vd);
std::cout << vd->point() << " [" << vertex_id_map[vd] << "]\n ";
}
return 0;
}