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Problem

Meeting Rooms II

LeetCode #253Medium
Chronological sweep · peak overlap = rooms

Given meeting time intervals, return the minimum number of conference rooms required — the maximum number of meetings that overlap at any single moment.

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[0,6]
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[5,8]
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Chronological sweep (events)
▸
1events ← split each meeting into (start,+1) and (end,−1)
2sort events by time; on ties, end before start
3rooms ← 0; peak ← 0
4for (time, +1) in events: rooms += 1
5for (time, −1) in events: rooms -= 1
6    peak = max(peak, rooms)
7return peak
state
  • meetings[0,6] [2,4] [5,8]

line 1Minimum rooms needed = the maximum number of meetings happening at the SAME time. Treat each meeting as a START event (+1 room) and an END event (−1 room).