Algorithm interview from Google

Question

I am a long time lurker, and just had an interview with Google where they asked me this question:

Various artists want to perform at the Royal Albert Hall and you are re

Answer 1

Store the number of used nights per year, quarter, and month. To find a free night, find the first year that is not fully booked, then the quarter within that year, then the month. Then check each of the nights in that month.

Irregularities in the calendar system makes this a little tricky so instead of using years and months you can apply the idea for units of 4 nights as "month", 16 nights as "quarter", and so on.