I'm not of Google, but big tech interviews are similar in a lot of ways, so yeah.

I've seen local candidates get interviews split over two days. You could probably ask for one split over several days, but not if the company is paying for a hotel. I dunno.

On my question, all the follow up work after the basics wouldn't make the rating go down. Other than like any sort of behavioral issues that came up; but I don't remember seeing anything like that; even from people we hired who later exhibited issues; they were able to keep it together during the interviews anyway.

The risk of intentionally stretching answers is that it might look like you've seen the problem before and are trying to hide it. My problem (and this problem) aren't really unique, although I didn't see too many people who had seemed to see it before; and my focus wasn't on the highly technical bits; the basics are quite simple, but there's a major downside to the simple solution with certain inputs, there's lots of ways to address that, I just want the candidate to come up with anything, it doesn't need to be the best, they don't need to know if it's the best, or how to know if it's the best, it really just needs to be complicated enough that the first code sample is more than 5 lines long; if we really ran through the problem in 10 minutes, we can spend some time exploring alternatives, but I'm not judging someone poorly because they did their way and can't think of seven others.