Meeting Rooms II

Given meeting intervals, print the minimum number of rooms required to hold all meetings. Input format: - First line: n - Next n lines: start end Intervals are half-open: a meeting ending at time t frees the room for a meeting starting at time t.

0 <= n <= 10^5
-10^9 <= start <= end <= 10^9

3
0 30
5 10
15 20

2

3
7 10
2 4
4 7

1