Meeting Rooms Minimum

Find the minimum number of meeting rooms needed to hold all intervals.

greedy intervals sorting

You are given a list of meeting time intervals, where each interval is a list [start, end] (with start < end). All times are integers. Meetings can start exactly when another meeting ends (i.e., intervals [1,3] and [3,5] can share the same room). Your task is to implement the function `min_meeting_rooms(intervals: list[list[int]]) -> int` that returns the minimum number of conference rooms required to host all meetings without any time overlap in the same room.

You must provide a solution that is efficient enough for large inputs and does not use external libraries.

Constraints

1 <= len(intervals) <= 10^5
0 <= start < end <= 10^9

Example

>>> min_meeting_rooms([[0,30],[5,10],[15,20]])
2
>>> min_meeting_rooms([[7,10],[2,4]])
1
>>> min_meeting_rooms([[1,5],[2,6],[3,7]])
3
>>> min_meeting_rooms([])
0

30 points ~25 min

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Hints

Think about time points: what events happen at each start and end?

Sort all start and end times separately, then use two pointers.

Alternatively, sort intervals by start time and maintain a min-heap of end times.

For each meeting, if the earliest ending meeting has ended, reuse that room; otherwise allocate a new room.

Test Results

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