Question
You are given `events`, a list of [user, timestamp] pairs (timestamps are integer seconds, NOT necessarily globally sorted, but per user they are non-decreasing in the order given). Group each user's events into sessions: a new session starts whenever the gap from the previous event of that same user exceeds `idle` seconds. Return a list of [user, session_count] sorted by user ascending. A user's first event always starts a session.
count_sessions(events: list[list], idle: int) → list[list][[["u1",0],["u1",10],["u1",100],["u2",5]],30]out[["u1",2],["u2",1]]State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.