This is concise and nice to read, but becomes very slow for large arrays. Taking (1..1000000).to_a as an input, took nearly 5 min on my (old) machine.

No problem at all! But thanks for the note (and for the kata :-). I've submitted a modified solution, using the new method name.

Sorry for the inconveniences I've changed method name to extract_file_name your solution will not pass from now. Please let me know if you want some other convention to be applied.

I'll keep that in mind, thanks a lot!

As a rule of thumb, never modify your inputs. Most langs have primitives that automatically "clone" but arrays are pretty much always mutable, so you should clone them before doing anything.

Oh, I see. I tried a recursive solution and didn't think about keeping the input array intact. Thanks for the pointer :-)

Don't modify the input array ;-)

I might be wrong, but it seems like the random tests (for Ruby) always expect the value of x as the return value.

Random tests
Testing for 12 and [712, 6636, 959, 81, 3734, 70, 1172, 33, 6, 561, 237, 749, 27, 74, 1, 7370, 8, 7335, 53, 5323]
It should work for random inputs too - Expected: 12, instead got: 143

No worries, thank you for your feed (I didn't think people could name a support function like me, but it was indeed pretty likely).

@myjinxin2015, we were editing the file in the same instant, I changed different things, apparentely; sorry for the inconvenience^^'

Yes, was talking about Ruby. Sorry for not mentioning the language.

Works like a charm now. Thanks for the quick fix!

It should be fixed.
Please re-test.
Thans for you feedback ;-)

I would assume it was for a naming collision: try now that I refactored, cheers :)

In Ruby?