mirror of https://github.com/CGAL/cgal
104 lines
3.2 KiB
C++
104 lines
3.2 KiB
C++
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
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#include <CGAL/Triangulation_2.h>
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#include <CGAL/boost/graph/graph_traits_Triangulation_2.h>
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#include <CGAL/boost/graph/dijkstra_shortest_paths.h>
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#include <boost/graph/filtered_graph.hpp>
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#include <fstream>
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typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
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typedef K::Point_2 Point;
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typedef CGAL::Triangulation_2<K> Triangulation;
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// As we want to run Dijskra's shortest path algorithm we only
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// consider finite vertices and edges.
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template <typename T>
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struct Is_finite {
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const T* t_;
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Is_finite()
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: t_(NULL)
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{}
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Is_finite(const T& t)
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: t_(&t)
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{ }
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template <typename VertexOrEdge>
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bool operator()(const VertexOrEdge& voe) const {
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return ! t_->is_infinite(voe);
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}
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};
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typedef Is_finite<Triangulation> Filter;
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typedef boost::filtered_graph<Triangulation,Filter,Filter> Finite_triangulation;
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typedef boost::graph_traits<Finite_triangulation>::vertex_descriptor vertex_descriptor;
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typedef boost::graph_traits<Finite_triangulation>::vertex_iterator vertex_iterator;
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typedef std::map<vertex_descriptor,int> VertexIndexMap;
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VertexIndexMap vertex_id_map;
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typedef boost::associative_property_map<VertexIndexMap> VertexIdPropertyMap;
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VertexIdPropertyMap vertex_index_pmap(vertex_id_map);
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int
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main(int argc,char* argv[])
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{
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const char* filename = (argc > 1) ? argv[1] : "data/points.xy";
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std::ifstream input(filename);
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Triangulation t;
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Filter is_finite(t);
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Finite_triangulation ft(t, is_finite, is_finite);
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Point p ;
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while(input >> p){
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t.insert(p);
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}
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vertex_iterator vit, ve;
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// Associate indices to the vertices
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int index = 0;
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// boost::tie assigns the first and second element of the std::pair
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// returned by boost::vertices to the variables vit and ve
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for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
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vertex_descriptor vd = *vit;
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vertex_id_map[vd]= index++;
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}
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// Dijkstra's shortest path needs property maps for the predecessor and distance
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// We first declare a vector
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std::vector<vertex_descriptor> predecessor(boost::num_vertices(ft));
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// and then turn it into a property map
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boost::iterator_property_map<std::vector<vertex_descriptor>::iterator,
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VertexIdPropertyMap>
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predecessor_pmap(predecessor.begin(), vertex_index_pmap);
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std::vector<double> distance(boost::num_vertices(ft));
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boost::iterator_property_map<std::vector<double>::iterator,
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VertexIdPropertyMap>
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distance_pmap(distance.begin(), vertex_index_pmap);
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// start at an arbitrary vertex
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vertex_descriptor source = *boost::vertices(ft).first;
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std::cout << "\nStart dijkstra_shortest_paths at " << source->point() <<"\n";
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boost::dijkstra_shortest_paths(ft, source,
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distance_map(distance_pmap)
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.predecessor_map(predecessor_pmap)
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.vertex_index_map(vertex_index_pmap));
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for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
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vertex_descriptor vd = *vit;
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std::cout << vd->point() << " [" << vertex_id_map[vd] << "] ";
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std::cout << " has distance = " << boost::get(distance_pmap,vd)
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<< " and predecessor ";
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vd = boost::get(predecessor_pmap,vd);
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std::cout << vd->point() << " [" << vertex_id_map[vd] << "]\n ";
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}
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return 0;
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}
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