This problem was asked by Twitter.
You run an e-commerce website and want to record the last
order ids in a log. Implement a data structure to accomplish this, with the following API:
record(order_id): adds the order_id to the log
get_last(i): gets the ith last element from the log. i is guaranteed to be smaller than or equal to N.
You should be as efficient with time and space as possible.