Meeting Rooms II

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), find the minimum number of conference rooms required.

Example:

• Input: [[0,30],[5,10],[15,20]]
• Output: 2
• Explanation: Meeting 1 (0-30) requires a room. Meeting 2 (5-10) overlaps, so it needs a new room. Meeting 3 (15-20) also overlaps with Meeting 1, but it starts after Meeting 2 ends, so it can reuse Meeting 2's room.

To minimize rooms, we want to "recycle" rooms as soon as they become free.

1. Sort: Sort meetings by start time.
2. Min-Heap (Priority Queue): Use a Min-Heap to store the end times of active meetings. The size of the heap represents the number of rooms currently in use.
3. Process: For each meeting:
   • Check the room that finishes earliest (top of Min-Heap).
   • If top <= current.start, that room is free! Poll the heap (remove top) to reuse it.
   • Push the current.end to the heap (representing the room now occupied until current.end).
4. Result: The size of the heap at the end (or max size reached) is the answer.

Alternatively, Chronological Ordering method (Sort Starts and Ends separately) also works.