> I guess even an off hand example, now must be completely 100% technically correct , or you aren't worth a job?

It's a litmus test, and not a terribly challenging one. It's solved by spending a week doing simple coding challenges.

Just use python for all practical programming problems. Lists, sets, and dicts are all you need for most leetcode problems; dynamic typing is convenient; there's good ergonomics for http and other random utility tasks; and pretty much every company is cool with python in an interview. You'll probably only see language trivia questions for languages you claim a specialty in (there's a huge market for C++ specialists, for instance).

Leetcode/hackerrank problems aren't that high variance, dedicate a weekend studying and you should be good.