Triangulation_2: Add an example that stars a conflict zone

Triangulation_2/doc/Triangulation_2/examples.txt

@@ -22,4 +22,5 @@
 \example Triangulation_2/segment_soup_to_polylines.cpp
 \example Triangulation_2/draw_triangulation_2.cpp
 \example Triangulation_2/low_dimensional.cpp
+\example Triangulation_2/star_conflict_zone.cpp
 */

Triangulation_2/examples/Triangulation_2/CMakeLists.txt

@@ -17,6 +17,7 @@ endforeach()
 
 if(CGAL_Qt5_FOUND)
   target_link_libraries(draw_triangulation_2 PUBLIC CGAL::CGAL_Basic_viewer)
+    target_link_libraries(star_conflict_zone PUBLIC CGAL::CGAL_Basic_viewer)
 else()
   message(
     STATUS

Triangulation_2/examples/Triangulation_2/star_conflict_zone.cpp

@@ -0,0 +1,59 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Delaunay_triangulation_2.h>
+#include <CGAL/draw_triangulation_2.h>
+#include <CGAL/spatial_sort.h>
+#include <array>
+#include <vector>
+#include <iostream>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_2 Point_2;
+typedef CGAL::Delaunay_triangulation_2<K>  Dt2;
+typedef Dt2::Edge Edge;
+typedef Dt2::Face_handle Face_handle;
+typedef Dt2::Face_circulator Face_circulator;
+typedef Dt2::Vertex_handle Vertex_handle;
+
+int main( )
+{
+  Dt2 dt2;
+
+  dt2.insert(Point_2(0,0));
+  dt2.insert(Point_2(10,0));
+  dt2.insert(Point_2(0,10));
+
+  std::array<Point_2,3> points = { Point_2(2,2), Point_2(1,0), Point_2(9,9) };
+
+  CGAL::spatial_sort(points.begin(), points.end());
+
+  Face_handle hint;
+
+  std::vector<Face_handle> faces;
+  std::vector<Edge> edges;
+
+  assert(dt2.dimension() == 2); // precondition of get_conflicts_and_bounda
+  for(const Point_2 p : points){
+    faces.clear(); // faster than variables in the scope
+    edges.clear();
+    dt2.get_conflicts_and_boundary(p,
+                                   std::back_inserter(faces),
+                                   std::back_inserter(edges),
+                                   hint);
+
+    // Do something with the faces before the insertion
+
+    Vertex_handle vh = dt2.star_hole(p,
+                                     edges.begin(), edges.end(),
+                                     faces.begin(), faces.end());
+    hint = vh->face(); // we could also take any element of faces
+
+    // Do something with the faces after the insertion
+    Face_circulator fc = dt2.incident_faces(vh), done(fc);
+    do {
+        fc++;
+    } while (fc != done);
+
+    draw(dt2);
+  }
+  return 0;
+}