Mid-levelMid (3–6 yrs)CodingPythonAmazonMetaBloomberg

Meeting Rooms II

Given meeting time intervals, find the minimum number of conference rooms required.

Answers use simple, clear English.

Audio N/A

Time: O(n log n)Space: O(n)

Quick interview answer

Sort starts and ends separately (or use a min-heap of end times). Sweep: increment on start, decrement on end; track peak concurrent meetings.

Detailed answer

Sort starts and ends separately (or use a min-heap of end times). Sweep: increment on start, decrement on end; track peak concurrent meetings. Equivalent to maximum overlap of intervals.

Full explanation

Equivalent to maximum overlap of intervals.

Real example & use case

Office booking system sizing how many Zoom rooms to reserve for a day.

Pros & cons

Pros: O(n log n). Cons: tie-breaking when start==end needs a policy (end first).

Code example

import heapq

def min_meeting_rooms(intervals: list[list[int]]) -> int:
    if not intervals: return 0
    intervals.sort()
    ends = []
    for s, e in intervals:
        if ends and ends[0] <= s:
            heapq.heappop(ends)
        heapq.heappush(ends, e)
    return len(ends)

Practice code · python (view only · no execution)

import heapq

def min_meeting_rooms(intervals: list[list[int]]) -> int:
    if not intervals: return 0
    intervals.sort()
    ends = []
    for s, e in intervals:
        if ends and ends[0] <= s:
            heapq.heappop(ends)
        heapq.heappush(ends, e)
    return len(ends)

#heap#intervals