O(log n) algorithm

2 passes, 1 sort

That would be an appropriate solution. As users will not lose ranking points if, for instance, this kata would get retired as a result of a deduplication process.

There actually needs to be a deduplication about this kind of kata, so maybe the rank can be handled then, by keeping a kata which is more appropriate.

I wouldn't start a witch hunt on old kata's. Is it that important to you this kata gets its ranking realigned by todays standards?

Yes you are right, that's a call for an admin

well it's from 2014, ranks have seriously deflated since then ... and they cannot be changed, at least not by regular users

That was fun.

Definitely not a 5-kyu kata, more like a 7-kyu one.
Some wrong votes happen

Erratum: 5/3

Golfed solution here

115 characters

Talking about code golfing for sure... ;-)

had a spasm reading this.

Average man: "Mine is longer!". Python developer: "Mine is shorter!"