How should I practice Longest Consecutive Login Streak?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Amazon onsite interview problems in FastPrep.

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Longest Consecutive Login Streak

Amazon● MediumNEW GRADONSITE INTERVIEW

Problem statement

Source note: A new-grad candidate for an entry-level software engineer role at Amazon described a virtual onsite of four one-hour rounds. In the second round the coding task was to take a list of user login records, each a user ID and a date, and find the longest run of consecutive login days, where a break of more than one day starts the count over. The report gives one sample record and no expected output, signature or limits, and it does not say whether the answer is per user or for everyone. In a reply the author said one of the three coding questions was probably object-oriented design but did not say which one.

Practice choices: the answer is the longest streak of any single user, so different users' logins are never joined; consecutive means the next calendar day, so even one missed day ends a streak; several logins on the same day count once; the records can be in any order; dates are real calendar dates from 2000 to 2099, so month ends, leap years and new year must be handled; the function returns one number of days; and the size limits and all three examples are ours. The task is practiced as a judged function rather than a class design.

The judged task matches the report at about 80%.

You are given a list of login records logins. Each record is [userId, date]: the user userId logged in on the day date, written as YYYY-MM-DD. The records can be in any order, and the same user can log in more than once on the same day.

A login streak of a user is a run of consecutive calendar days on which that user logged in at least once. If the user misses a day, the streak ends, and the next login starts a new streak. Several logins on one day count as one day.

The problem statement continues

Pro

Examples

Example 1

logins = [["ana","2026-05-03"],["ben","2026-05-03"],["ana","2026-05-04"],["ana","2026-05-06"],["ben","2026-05-04"],["ben","2026-05-05"],["ana","2026-05-07"],["ana","2026-05-08"]]return = 3

ana logs in on May 3 and 4, misses May 5, then logs in on May 6, 7 and 8. Her longest run is May 6 to May 8, which is 3 days. ben logs in on May 3, 4 and 5, also 3 days. The answer is 3.

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