Is there a robust C++ implementation of the Bentley-Ottmann algorithm?

Question

The Bentley-Ottoman algorithm finds all crossings in a set of line segments. For a well known and important algorithm, it seems quite weird that a C++ implementation of Bent

Answer 1

CGAL has something in there with the same complexity as Bentley-Ottmann, O((n + k)*log(n)) where n is the number of segments and k is the number of intersections (not sure which algorithm they used):

//! \file examples/Arrangement_on_surface_2/sweep_line.cpp
// Computing intersection points among curves using the sweep line.

#include 
#include 
#include 
#include 
#include 
#include 

typedef CGAL::Quotient                  NT;
typedef CGAL::Cartesian                             Kernel;
typedef Kernel::Point_2                                 Point_2;
typedef CGAL::Arr_segment_traits_2              Traits_2;
typedef Traits_2::Curve_2                               Segment_2;

int main()
{
  // Construct the input segments.
  Segment_2 segments[] = {Segment_2 (Point_2 (1, 5), Point_2 (8, 5)),
                          Segment_2 (Point_2 (1, 1), Point_2 (8, 8)),
                          Segment_2 (Point_2 (3, 1), Point_2 (3, 8)),
                          Segment_2 (Point_2 (8, 5), Point_2 (8, 8))};

  // Compute all intersection points.
  std::list     pts;

  CGAL::compute_intersection_points (segments, segments + 4,
                                     std::back_inserter (pts));

  // Print the result.
  std::cout << "Found " << pts.size() << " intersection points: " << std::endl; 
  std::copy (pts.begin(), pts.end(),
             std::ostream_iterator(std::cout, "\n"));

  // Compute the non-intersecting sub-segments induced by the input segments.
  std::list   sub_segs;

  CGAL::compute_subcurves(segments, segments + 4, std::back_inserter(sub_segs));

  std::cout << "Found " << sub_segs.size()
            << " interior-disjoint sub-segments." << std::endl;

  CGAL_assertion (CGAL::do_curves_intersect (segments, segments + 4));

  return 0;
}

http://doc.cgal.org/latest/Sweep_line_2/index.html