Questions about off-site programming challenges, such as those featured on Project Euler, Hackerrank, etc., are off topic here. However, it's come to my attention recently that questions about such challenges are actually on topic on Code Review. Indeed, they even have a dedicated tag for such questions. As such, I propose that we add a new close reason that suggests that the OP check out Code Review, akin to our current option for general programming questions, which suggests Stack Overflow:
This site is for programming contests and challenges. General programming questions are off-topic here. You may be able to get help on Stack Overflow.
It could say something along the lines of
This site is for creating and participating in programming contests and challenges. Questions about off-site programming challenges are off-topic here. You may be able to get help on Code Review.
To clarify, we would of course still direct folks without working code to Stack Overflow, and ensure that only questions that could be on topic for Code Review (with a recommendation to check out their Help Center as needed, as we currently do for SO) be suggested for Code Review.