It would actually probably count as a derivative work under US copyright law. (Don't misread me: I do not endorse, condone, or make excuses for US copyright law. I'm just describing it).

edit: Here's an example,

- "In so doing, the magistrate judge agreed with plaintiffs’ assertion that the solution manuals sold by defendant qualified as “derivative works” under the Copyright Act. As in Pavlica v. Behr and Addison-Wesley Publ’g Co. v. Brown, defendant’s manuals complemented plaintiffs’ 187 copyrighted textbooks, had no “independent economic value” and were “meaningless’ without the textbooks because they merely provided answers to questions posed in the textbooks."

https://www.law.com/newyorklawjournal/almID/1202435027834/ (2009)

https://www.courtlistener.com/docket/4345754/pearson-educati... (the ruling is available here, gratis)

IANAL but I believe the case is different for algorithmic solutions.

The solutions to a particular textbook are entirely useless outside the context of the textbook, but the solution to "efficiently find a substring within a string" is useful in day-to-day programming. The takedown isn't aimed at the result of "convert 700m to feet", but "describe the process of converting between metres and feet", which is plain ridiculous.

Yeah this stood out to me too. If I publish code that I wrote for no remuneration, how does HackerRank claim to own the copyright to that code?

They explicitly don’t. See this: https://www.hackerrank.com/terms-of-service

Is someone going to start asserting copyright over people's varied fizzbizz solutions? Fucking bonkers!