(Assuming atp means 'at this point')

Hm, I am not sure. Maybe? :) But there will always be three elements to concatenate on every line.

I personally try to avoid lambdas (unless needed for higher order functions), but that is a matter of taste.

why not using lambda and join atp? (i don't know if it's actually possible, but i think it should be just by looking at how you used the return)

Not a good practice to use exceptions for implementing normal program flow.

Exactly how I did it :)

you best

Did this lmao

I knew it!

You are correct. =) But I solve katas for fun, and sometimes that goes against best practises.

Putting the whole function in one line may be clever, but it's not best practices.

Yep, this is O(n²) for the reason you explained.
And I disagree with RazNaot, just because you can solve a problem inefficiently doesn't mean you should. The goal of this website is to improve at programming.

Oh, I see. Thank you.

The custom in this site for the easier katas, is not to be restricted by performance and memory constraints. At most katas leveled kyu 8 to kyu 6, almost all algorithms will work. They are meant to be easy training, with fewer and smaller test cases - so just do something that works and you'll pass. The harder katas - around kyu 5,4 and up may require "performance" - i.e. slower algos may fail etc. Browse "Kata" on the top left menu to get to harder questions...

Did anyone check the complexity of this solution?
It's very short and nice, but is it optimal in terms of CPU/RAM usage?
As I can see we will get one list traversal for getting a set. Then we will get a traversal per each element in the set. Which i think is suboptimal.
Thoughts?