Earlier quoted context omitted.
Reportedly, Carmack did it an a week by locking himself in an hotel room
If he could've done it in a week then he didn't really need to do it at all.
Of course not being able to ask someone any questions would be disadvantage (but is that even a 'rule' of this scenario? Surely at least the internet is allowed, i.e. a person to ask who's available to anyone), and it would have been a lot easier while at university than with X years' rust on the background maths etc. - but still, seven full days is a lot of time if you choose to completely dedicate it to some particular thing, we just generally don't do that, so it doesn't sound it.