This was fun, thank you!

Pretty challenging kata of the series, nice one.

You will get the same final answer regardless of which i and j you choose for each iteration, so long as X[i] > X[j].

Thanks! I like to write in functional style when possible and next in Python is very useful for that. However, after 2 years it took me a moment to understand what that accumulate does.

Agreed on moving the 4 into cycle, it saves a lot of multiplications (though s was meant to represent the sign, expressed with +1 or -1).

I prefer to use math.isclose instead of abs to check if the floating point numbers are close because I can quickly recognize what that code is doing, but your mileage may vary.

and you neither have to sort the arrays but fill the appropriate count of values instead. But I guess than it becomes more verbous (not an expert on Python's syntactic sugar)

My solution in Python reaches the "rectangles have only common faces (version 2)" random test then times out. Ported to Javascript, it passes in approx. 9 seconds.

Nice kata despite the clunky description. I did not even try to brute-force the solution because I thought it would time out (my bad). I ended up writing a solution that works for more general cases.

This was fun, thank you! I am particularly happy with the way I achieved numerical stability in Python.

That's clever! It confirms that 55-character limit and return type integer could both be enforced.

There is room to cast it to integers.

I asked myself the same question, this is not an easy kata to rank. I would say 5-kyu or 4-kyu if the number of islands in the test was choosen so that all brute-force solutions fail, but any "textbook" implementation of the correct algorithm succeeds, regardless of language-dependant optimizations.

If the implementation must be optimized (i.e. choosing the right data structure) in consideration of the high "density" of the bridges, then definitely 4-kyu, but it is not clear to me if that's what you required.

A performance edition could be created (2-kyu maybe) where the number of bridges is so high that some upfront reduction is necessary (see my other comment hidden as spoiler) leveraging the 2D nature of the points representing the islands.

...and that's how you disregard PEP8 with flair 😀

Congrats! And thank you for the kind words.

Yes, I picked the maximum number of islands carefully 😈

Out of interest, what kyu rating would you give it?