Python and SQL Analytics Thought Exercise | Dataford Interview Questions

Tell me about a time you worked through an analytics thought exercise involving SQL and coding.

Given activity records containing a user ID and day, return the users who have at least one record on every day in an inclusive interval. Duplicate records must not inflate coverage. Return user IDs in lexicographic order.

Input and Output

records is a list of [user_id, day] pairs. start_day and end_day are integers. Return a list of strings.

Example: records = [["u1", 1], ["u1", 2], ["u2", 1], ["u1", 2]], start_day = 1, end_day = 2 returns ["u1"], because the duplicate day-2 record does not replace missing coverage for another user.

Constraints

1 <= len(records) <= 5000
1 <= start_day <= end_day <= 10^9
Each record has the form [user_id, day]
user_id is a non-empty string
1 <= day <= 10^9

Function Signature

def users_active_every_day(records, start_day, end_day):

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