Arrangement_on_surface_2/circles.cpp

// Constructing an arrangement of circles using the conic-arc traits.

#include <CGAL/Cartesian.h>
#include <CGAL/Exact_rational.h>
#include <CGAL/Arr_circle_segment_traits_2.h>
#include <CGAL/Arrangement_2.h>

typedef CGAL::Cartesian<CGAL::Exact_rational>         Kernel;
typedef Kernel::Circle_2                              Circle_2;
typedef CGAL::Arr_circle_segment_traits_2<Kernel>     Traits_2;
typedef Traits_2::CoordNT                             CoordNT;
typedef Traits_2::Point_2                             Point_2;
typedef Traits_2::Curve_2                             Curve_2;
typedef CGAL::Arrangement_2<Traits_2>                 Arrangement_2;

int main()
{
  // Create a circle centered at the origin with radius 5.
  Kernel::Point_2 c1 = Kernel::Point_2(0, 0);
  CGAL::Exact_rational sqr_r1 = CGAL::Exact_rational(25);       // = 5^2
  Circle_2 circ1 = Circle_2(c1, sqr_r1, CGAL::CLOCKWISE);
  Curve_2 cv1 = Curve_2(circ1);

  // Create a circle centered at (7,7) with radius 5.
  Kernel::Point_2 c2 = Kernel::Point_2(7, 7);
  CGAL::Exact_rational sqr_r2 = CGAL::Exact_rational(25);       // = 5^2
  Circle_2 circ2 = Circle_2(c2, sqr_r2, CGAL::CLOCKWISE);
  Curve_2 cv2 = Curve_2(circ2);

  // Create a circle centered at (4,-0.5) with radius 3.5 (= 7/2).
  Kernel::Point_2 c3 = Kernel::Point_2(4, CGAL::Exact_rational(-1,2));
  CGAL::Exact_rational sqr_r3 = CGAL::Exact_rational(49, 4);    // = 3.5^2
  Circle_2 circ3 = Circle_2(c3, sqr_r3, CGAL::CLOCKWISE);
  Curve_2 cv3 = Curve_2(circ3);

  // Construct the arrangement of the three circles.
  Arrangement_2 arr;

  insert(arr, cv1);
  insert(arr, cv2);
  insert(arr, cv3);

  // Locate the vertex with maximal degree.
  Arrangement_2::Vertex_const_iterator vit;
  Arrangement_2::Vertex_const_handle v_max;
  std::size_t max_degree = 0;

  for (vit = arr.vertices_begin(); vit != arr.vertices_end(); ++vit) {
    if (vit->degree() > max_degree) {
      v_max = vit;
      max_degree = vit->degree();
    }
  }

  std::cout << "The vertex with maximal degree in the arrangement is: "
            << "v_max = (" << v_max->point() << ") "
            << "with degree " << max_degree << "." << std::endl;
  return 0;
}