Cool! But what about complexity of your algorithm? Instead of O(n), you seems to have O(n*log(n)).

I like the solution provided by jakalm, but you are right and your comment about range is reasonable. The approximation starts failing somewhere in range 8e8 < beer_count < 9e8.

There are specifications:

input customers: an array of positive integers representing the queue.

So a (silly and absurd) input of a negative queue will never happen.

Very nice! However, it will crash when (n <= 0).