Probably but if those are the only two areas you want to see, that's a huge waste of money. There are no discounts for single day admission and you will have to purchase a park to park ticket. Are you not going to see other attractions in both parks? You won't be able to do everything but you could do the highlights.Do you predict one day would be enough to visit both Diagon Alley and Hogsmeade on Tuesday the 9th in December?
Two days would definitely be better...if you have the time.We'll probably want to do a few attractions like Springfield for the Simpsons. So probably 2 days huh?