Stackoverflow is clearly not a "plz [sic] fix my code" website.
You can see comments to that effect, and code just dumped in there is quickly down voted. Do we allow
plz fix des codez questions here?
The purpose of this site is to support the learning process for cs50x students. Simply fixing someone's code with no explanation is a poor way to help someone learn. However, it's up to the user who answers a question to decide how they want to answer, what sort of explanation they give, and whether to provide an exact solution to the question author's problem.
In my opinion, answers that do nothing but fix code work against the goal of helping students learn. I downvote those answers and I don't think they belong on this site. I have also voted to close questions like this one as being off topic and I stand by those votes.
However, practically speaking, there are not enough active reviewers to close these questions in a timely fashion. Plus, it's a judgment call which questions are "good enough" to fly—here is an example of a question that has attracted a high-quality answer despite being mainly a request for debugging help. (In terms of the questions, the difference between this one and the one I voted to close is that the author here has clearly identified the expected behavior, the desired behavior and how they are different.)
The audience of this site is very different from that of Stack Overflow. I've said before that there's no reason we should blindly enforce another site's scoping rules on this site and I think that's true generally across the Stack Exchange network. We've had similar discussions about dealing with questions where the author seems to only want someone to fix their problem. Our main issue is that we lack moderation resources and policy guidance.
My advice would be to downvote aggressively to send the message that a question needs to be improved, but be more judicious with your close votes. If we had more moderation resources I'd say close them ASAP, so that the author has a stronger incentive to improve the question; as things stand it's unlikely we'll ever drum up the votes to reopen a question once it's closed, so save your close votes for questions that really couldn't get a high quality answer that addresses a distinct, searchable topic. Most of the time you can close these as unclear or too broad, which is a much better way to communicate to the author what they did wrong than telling them their question about a cs50 problem set is off-topic on the cs50 Q&A site.