I had Uber phone screen last week after OA.

I was told it was leetcode style problem for this 60-minute interview. At the beginning, interviewer sort of spent 15 minutes to go over the resume / past experience. The rest is for a leetcode medium question.

Question: Implement a Counter class that has the following methods:

1. put(number): put the number to the data structure
2. count(number): count the number of times number was put during the last window=5 minutes
3. countAll(): count the number of times any number was put during the last window=5 minutes.

Example:
At t = 10PM, put(2)
At t = 10:02PM, put(2)
At t = 10:03PM, put(3)
At t = 10:04PM, count(2) should return 2
At t = 10:04PM, countAll() should return 3
At t = 10:06PM, count(2) should return 1 (the one that was put at 10:02PM)
At t = 10:06PM, countAll() should return 2

Follow-ups:

1. If you were to write unit tests, what would they be
2. If your code was to be in production, what issues may it cause?

I'm going to onsite.