## Description

https://leetcode.com/problems/meeting-rooms-ii/

Given an array of meeting time intervals consisting of start and end times `[[s1,e1],[s2,e2],...]`

(s_{i} < e_{i}), find the minimum number of conference rooms required.

**Example 1:**

Input:`[[0, 30],[5, 10],[15, 20]]`

Output:2

**Example 2:**

Input:[[7,10],[2,4]]Output:1

**NOTE:** input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.

## Explanation

heap

## Python Solution

```
class Solution:
def minMeetingRooms(self, intervals: List[List[int]]) -> int:
if not intervals:
return 0
free_rooms = []
intervals = sorted(intervals, key=lambda interval: interval[0])
heapq.heappush(free_rooms, intervals[0][1])
for interval in intervals[1:]:
if free_rooms[0] <= interval[0]:
heapq.heappop(free_rooms)
heapq.heappush(free_rooms, interval[1])
return len(free_rooms)
```

- Time Complexity: ~Nlog(N)
- Space Complexity: ~N