CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 06/06/2014 03:46 PM, Michael SCHINDLER wrote:
> Dear list,
>
> I am rather new to CGAL, trying to use the weighted Delaunay and
> periodic triangulations. At the moment, I have a technical question on
> Union_find which I use to identify classes of triangulation vertices.
>
> Once I have unified the sets in my Union_find instance, by
> something like
>    CGAL::Union_find<Vertex_handle> cls;
>    CGAL::Unique_hash_map<Vertex_handle, typename 
> CGAL::Union_find<Vertex_handle>::handle> cl_items(NULL);
>    ... and then for some vertex handle vv0, vv1 ...
>    cls.unify_sets(cls.find(cl_items[vv0]), cls.find(cl_items[vv1]));
>
> I would like to iterate over all sets in cls, which can be done with
> the iterator given Union_find::iterator. But how can I then iterate
> over the members of such a set?
The only method I know is to filter the iterator range using same_set
or to go over the iterator once and dispatch the element in another
container.

> BTW: Is there a more elegant way to use unify_sets without the
> search in a Unique_hash_map?
Well, if you extend the vertex type to get an id field (using 
Triangulation_vertex_base_with_info_3 for example) then you
could use a std::vector to store the handle and get direct
access to the handles.

See some examples here:
http://doc.cgal.org/latest/Triangulation_3/index.html#title13

Sebastien

> Thanks in advance for any advice,
> Michael Schindler