103 lines
3.3 KiB
C++
103 lines
3.3 KiB
C++
#include <CGAL/Simple_cartesian.h>
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#include <CGAL/Polygon_2.h>
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#include <CGAL/create_straight_skeleton_2.h>
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#include <CGAL/number_utils.h>
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#include <boost/multiprecision/cpp_int.hpp>
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#include <boost/multiprecision/number.hpp>
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#include <boost/multiprecision/rational_adaptor.hpp>
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#include <iostream>
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#include <sstream>
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#include <string>
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#include <memory>
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#include <iomanip>
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// Use exact rational arithmetic throughout to avoid filtered predicates
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typedef boost::multiprecision::number<boost::multiprecision::rational_adaptor<boost::multiprecision::cpp_int_backend<>>> Exact_NT;
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typedef CGAL::Simple_cartesian<Exact_NT> Exact_K;
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// Input kernel with doubles for reading coordinates
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typedef CGAL::Simple_cartesian<double> Input_K;
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// Use exact kernel for computation
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typedef Exact_K K;
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typedef K::Point_2 Point;
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typedef CGAL::Polygon_2<K> Polygon_2;
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typedef CGAL::Straight_skeleton_2<K> Ss;
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typedef std::shared_ptr<Ss> SsPtr;
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int main()
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{
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Polygon_2 poly;
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std::string line;
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while (std::getline(std::cin, line)) {
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if (line.empty()) {
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continue;
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}
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std::istringstream iss(line);
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double x, y;
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if (iss >> x >> y) {
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// Convert double to exact rational
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poly.push_back(Point(Exact_NT(x), Exact_NT(y)));
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} else {
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std::cerr << "Error: Invalid input line: " << line << std::endl;
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return EXIT_FAILURE;
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}
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}
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if (poly.size() < 3) {
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std::cerr << "Error: Polygon must have at least 3 vertices" << std::endl;
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return EXIT_FAILURE;
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}
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if (!poly.is_counterclockwise_oriented()) {
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std::cerr << "Error: Polygon must be counter-clockwise" << std::endl;
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return EXIT_FAILURE;
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}
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SsPtr ss = CGAL::create_interior_straight_skeleton_2(poly.vertices_begin(), poly.vertices_end(), K());
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if (!ss) {
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std::cerr << "Error: Failed to create straight skeleton" << std::endl;
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return EXIT_FAILURE;
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}
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// Output skeleton edges
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// Iterate through all halfedges in the skeleton
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for (auto he = ss->halfedges_begin(); he != ss->halfedges_end(); ++he) {
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// Only output each edge once (skip the opposite halfedge)
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if (he->id() < he->opposite()->id()) {
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continue;
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}
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// Get the vertices at both ends of the halfedge
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auto v_source = he->vertex();
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auto v_target = he->opposite()->vertex();
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// Get times (distance from boundary)
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// Convert from exact rational to double for output
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double t1 = CGAL::to_double(v_source->time());
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double t2 = CGAL::to_double(v_target->time());
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// Skip contour edges (outline of the input polygon)
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// Contour edges have both vertices at time 0
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if (t1 == 0.0 && t2 == 0.0) {
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continue;
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}
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// Get coordinates
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double x1 = CGAL::to_double(v_source->point().x());
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double y1 = CGAL::to_double(v_source->point().y());
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double x2 = CGAL::to_double(v_target->point().x());
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double y2 = CGAL::to_double(v_target->point().y());
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// Output: start_x start_y end_x end_y start_time end_time
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std::cout << std::setprecision(12) << x1 << " " << y1 << " "
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<< x2 << " " << y2 << " "
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<< t1 << " " << t2 << std::endl;
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}
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return EXIT_SUCCESS;
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}
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