code wars is ruined by the 13 to 20 demographic

I like the logic behind your solution. Very similar to mine

this is not performant. it goes over list multiple times

This is a smart one.

No but tests guarantee that there is ever only two different numbers, one of them unique.

It would indeed.

That's what I've done.

Guys will that work if there is two different uniq numbers?

wow, smart one

but if arr has three uniq numbers, Could your function run? I think it not real nice

Because your post is visible in the homepage if you don't do it for people who still hasn't solved the kata and you posted a solution in your post. That's why.

why?

Please use spoiler flag next time.

I use the "Fork" button, then "Run" and it shows the time. There can be quite a bit of variation between separate runs of the same code though.