thank you very much. I finally figured it out

It is a non capturing group, so you can group a set of characters and optionalise them. https://www.stefanjudis.com/today-i-learned/non-capturing-groups-in-regular-expressions/

that doesn't change anything

It's a magic))

I used regex instead but the 0.5 it's more readable and simple, I need to wash my brain or something bc I usually don't see theese kind of solutions

Exactly.

then it's just Hardcoding?

No.

Is this cheating ? xd

what background do you need to make algorithms like this? (besides from algorithms ofc) I want to study but I'm not sure where and how. I did this with recursion but it probably has a big time complexity

where's the dude complaining about using sort(); lol

Doesn't work with [23,12,56,2,80], should be [56,80]

I also don't know, Maybe it's more fast on the sum ? lol