Given meeting time intervals, find the minimum number of conference rooms required.
With intervals = [[0,30],[5,10],[15,20]]:
- Meeting [0,30] needs a room.
- At time 5, meeting [5,10] starts. [0,30] is ongoing. Need rooms.
- At time 15, meeting [15,20] starts. [0,30] still ongoing. Still rooms.
- Maximum concurrent: rooms.
With intervals = [[7,10],[2,4]]:
- [2,4] ends at 4. [7,10] starts at 7.
- Never overlapping. room suffices.
Constraints: intervals.length .