I am surprise because I tought everyone used the way I used but seen none.
Was the way I did the way it was intented ?

Yes, most-connected-to is not a way to go. You need to think of something different.

Did not like this AT ALL. Guessing at algo, I went thru hassle of removing
most-connected-to-nodes, but at end, if there's a diamond,
impossible to tell inner from outer.

There's a few possibilities, and ASCII drawings is one of them :)

There is also embedded SVG.

Yes, that's your problem, they are quite fine on my side.

but description should not rely on external resouces.

Then what's the resort? Make ASCII arts?

.

@dolamroth: see the issue above, plz

why is it a set while JS expects a sorted array??

Python: return type should be set, but initial solution returns a dict: {}.

Images are not loaded.

Maybe it's a temporary problem, but description should not rely on external resouces.

Yeah, and I coded up a Python solution using your logic in just 5 minutes. So simple and elegant.

Thanks for the compliment. I checked your septagonal disc shape (nice one, btw) against this, and it indeed returns all vertices, as expected.

Yeah that makes entirely new sense now. Actually that's really clever and, as far as I can tell, totally correct.

Here's a septagonal disc shape (with a "hole" in the middle), the odd numbers are the outer perimiter, the even numbers the inner perimiter:

triangles = [(1,2,3), (2,3,4), (3,4,5), (4,5,6), (5,6,7), (6,7,8), (7,8,9), (8,9,10), 
             (9,10,11), (10,11,12), (11,12,13), (12,13,14), (13,14,1), (14,1,2)]

All vertices should be "external", but my code returns the empty set. Of course, the hole could be interpreted as a closed internal septagon, depending on how the topology is defined, but if we just consider the triangles as polygons, then there should be two perimiters here.