You're right: most solutions here are O(n^2), but this one is O(n). The code duplication makes it read like a C program, so initially I was surprised.

You can work with as many languages as you like, but indeed, working with languages is missing some support:

• progress is already collected per language: https://docs.codewars.com/gamification/ranks#user-rank-breakdown
• there's no language leaderboards, but such feature has been requested. You can share your ideas here, if you have any: https://github.com/codewars/codewars.com/discussions/2371
• there's no direct support for marking or filtering completed kata by language, but there's unofficial workaround: https://github.com/codewars/codewars.com/discussions/2377
• It's not possible to have different difficulty rankings for translations of one kata. All language versions of one kata have the same difficulty rank.

Yeah I'm really interested in this feature as well