Frequent user events within a 24-hour window

You are given a list of activity log entries. Each entry has a user_id (string), a timestamp (integer seconds since epoch) and an event_type (string). The list is not sorted.

Implement:

def frequent_events(logs: list[LogEntry], k: int) -> list[str]: ...

Return, sorted alphabetically, every event type that some single user performed at least k times within a 24-hour window. A group of events fits in a 24-hour window when the time between its first and last event is strictly less than 86,400 seconds.

• Counts are per user. Two users doing the same event never add together.
• Entries with the same timestamp are separate events.
• 1 <= k, and there are up to 10^5 log entries.

Example 1 (k = 3, times in hours for readability)

Output: ["upload"]. Ana uploads 3 times within 19 hours. share happens 3 times in total, but ben does it only twice.

Example 2 (k = 2): one user logs export at 0h and again at exactly 24h. Output: [], because events exactly 24 hours apart are not inside the same window.

Be ready to discuss a streaming version where entries arrive one at a time.

Reconstructed from the reported question; details may differ from what interviewers ask.