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#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>
#include <CGAL/boost/graph/graph_traits_Delaunay_triangulation_2.h>
#include <CGAL/boost/graph/kruskal_min_spanning_tree.h>
#include <fstream>
#include <iostream>
#include <map>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_2 Point;
typedef CGAL::Delaunay_triangulation_2<K> Triangulation;
typedef boost::graph_traits<Triangulation>::vertex_descriptor vertex_descriptor;
typedef boost::graph_traits<Triangulation>::vertex_iterator vertex_iterator;
typedef boost::graph_traits<Triangulation>::edge_descriptor edge_descriptor;
// The BGL makes use of indices associated to the vertices
// We use a std::map to store the index
typedef std::map<vertex_descriptor,int> VertexIndexMap;
// A std::map is not a property map, because it is not lightweight
typedef boost::associative_property_map<VertexIndexMap> VertexIdPropertyMap;
int main(int argc,char* argv[])
{
const char* filename = (argc > 1) ? argv[1] : "data/points.xy";
std::ifstream input(filename);
Triangulation tr;
Point p;
while(input >> p)
tr.insert(p);
// Associate indices to the vertices
VertexIndexMap vertex_id_map;
VertexIdPropertyMap vertex_index_pmap(vertex_id_map);
int index = 0;
for(vertex_descriptor vd : vertices(tr))
vertex_id_map[vd] = index++;
// We use the default edge weight which is the squared length of the edge
// This property map is defined in graph_traits_Triangulation_2.h
// In the function call you can see a named parameter: vertex_index_map
std::list<edge_descriptor> mst;
boost::kruskal_minimum_spanning_tree(tr, std::back_inserter(mst),
vertex_index_map(vertex_index_pmap));
std::cout << "The edges of the Euclidean minimum spanning tree:" << std::endl;
for(edge_descriptor ed : mst)
{
vertex_descriptor svd = source(ed, tr);
vertex_descriptor tvd = target(ed, tr);
Triangulation::Vertex_handle sv = svd;
Triangulation::Vertex_handle tv = tvd;
std::cout << "[ " << sv->point() << " | " << tv->point() << " ] " << std::endl;
}
return EXIT_SUCCESS;
}
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