Find the Minimum Number of Meeting Rooms
Company: Bytedance
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: hard
Interview Round: Technical Screen
# Find the Minimum Number of Meeting Rooms
You are given meeting intervals `[start, end]`, where `start < end`. A room can host at most one meeting at a time, and a meeting ending at time `t` does not conflict with another meeting starting at time `t`.
Return the minimum number of rooms required to host every meeting.
## Function Signature
```python
def minimum_meeting_rooms(intervals: list[list[int]]) -> int:
...
```
## Constraints
- `0 <= len(intervals) <= 200_000`
- Every interval contains exactly two integer times between `-1_000_000_000` and `1_000_000_000`, inclusive.
- `start < end` for every meeting.
- Input intervals may be unsorted and may share start or end times.
## Examples
```text
Input: intervals = [[0, 30], [5, 10], [15, 20]]
Output: 2
```
```text
Input: intervals = [[7, 10], [10, 12]]
Output: 1
```
```text
Input: intervals = []
Output: 0
```
Quick Answer: Find the minimum number of rooms needed for unsorted meeting intervals, with an ending meeting allowed to share a room with one starting at the same time. Practice sweep-line or heap reasoning, precise tie handling, overlapping intervals, duplicate boundaries, empty input, and large-scale time complexity.