#134 Medium Time O(n log n) Space O(n) Animated

Meeting Rooms II

Find minimum number of conference rooms required.

LeetCode ↗

Tutor Mode Build the mental model before you memorize the code.

1 Predict
2 Trace
3 Explain
4 Implement

Pattern Sort intervals, then maintain one boundary

After sorting, overlap decisions depend only on the active interval and the next start.

Approach: Two Pointers (Start/End arrays)

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Core Insight

After sorting, overlap decisions depend only on the active interval and the next start.

Common Pitfall

Compare the next start against the current end, not against the original unsorted input.

Description

Find minimum number of conference rooms required.

Constraints

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

Solution — Two Pointers (Start/End arrays)

TimeO(n log n) SpaceO(n)

Implementation Plan

Translate the invariant into these small, testable moves.

Sort by the relevant endpoint.
Initialize the active interval.
Merge or select based on overlap.
Update the active boundary.

def minMeetingRooms(intervals):
    start = sorted([i[0] for i in intervals])
    end = sorted([i[1] for i in intervals])
    
    res, count = 0, 0
    s, e = 0, 0
    while s < len(intervals):
        if start[s] < end[e]:
            s += 1
            count += 1
        else:
            e += 1
            count -= 1
        res = max(res, count)
        
    return res

Meeting Rooms

Minimum Interval to Include Each Query

Meeting Rooms II

Steps

Description

Constraints

Tags

Solution — Two Pointers (Start/End arrays)