mirror of https://github.com/CGAL/cgal
110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
// Copyright (c) 2018 Inria
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// All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org)
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//
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// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
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//
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// Author(s) : Marc Glisse
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#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
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#include <CGAL/Delaunay_triangulation_2.h>
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#include <CGAL/CGAL_Ipelet_base.h>
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#include <CGAL/boost/graph/graph_traits_Delaunay_triangulation_2.h>
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#include <boost/graph/kruskal_min_spanning_tree.hpp>
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#include <boost/graph/filtered_graph.hpp>
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namespace CGAL_mst {
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typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
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typedef CGAL::Delaunay_triangulation_2<Kernel> Triangulation;
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const std::string Slab[] = {
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"MST", "Help"
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};
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const std::string Hmsg[] = {
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"Draw the minimum spanning tree of a set of points"
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};
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struct mstIpelet
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: CGAL::Ipelet_base<Kernel, 2> {
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mstIpelet() : CGAL::Ipelet_base<Kernel, 2>("Minimum spanning tree", Slab, Hmsg){}
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void protected_run(int);
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};
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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_(nullptr)
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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 boost::graph_traits<Finite_triangulation>::edge_descriptor edge_descriptor;
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// The BGL makes use of indices associated to the vertices
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// We use a std::map to store the index
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typedef std::map<vertex_descriptor,int> VertexIndexMap;
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VertexIndexMap vertex_id_map;
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// A std::map is not a property map, because it is not lightweight
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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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void mstIpelet::protected_run(int /*fn*/)
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{
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std::list<Point_2> pt_list;
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read_active_objects(
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CGAL::dispatch_or_drop_output<Point_2>(
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std::back_inserter(pt_list)
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)
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);
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if (pt_list.empty()) {
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print_error_message("No mark selected");
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return;
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}
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Triangulation t(pt_list.begin(), pt_list.end());
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Filter is_finite(t);
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Finite_triangulation ft(t, is_finite, is_finite);
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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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// We use the default edge weight which is the squared length of the edge
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// This property map is defined in graph_traits_Triangulation_2.h
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// In the function call you can see a named parameter: vertex_index_map
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std::list<edge_descriptor> mst;
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boost::kruskal_minimum_spanning_tree(ft,
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std::back_inserter(mst),
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vertex_index_map(vertex_index_pmap));
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for(std::list<edge_descriptor>::iterator it = mst.begin(); it != mst.end(); ++it){
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edge_descriptor ed = *it;
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vertex_descriptor svd = source(ed,t);
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vertex_descriptor tvd = target(ed,t);
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Triangulation::Vertex_handle sv = svd;
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Triangulation::Vertex_handle tv = tvd;
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draw_in_ipe(Kernel::Segment_2(sv->point(), tv->point()));
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}
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}
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}
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CGAL_IPELET(CGAL_mst::mstIpelet)
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