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

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.

For example,
Given [[0, 30],[5, 10],[15, 20]],
return 2.

# Definition for an interval.
class Interval(object):
    def __init__(self, s=0, e=0):
        self.start 
 
= s
        self.end = e

class Solution(object):
    def minMeetingRooms(self, intervals):
        """
        :type intervals: List[Interval]
        :rtype: int
        """
        
        intervals.sort(key = lambda x: x.start)
        # stores the end time of intervals
        heap = []
        
 
for i in intervals:
            if heap and i.start >= heap[0]:
                # means two intervals can use the same room
                heapq.heapreplace(heap, i.end)
            else:
                # a new room is allocated
                heapq.heappush(heap, i.end)
        return len(heap)

Note:

1 heapq.heappop() in python can pop the smallest value in the heap. Here‘s the demo.

import heapq

h = []

heapq.heappush(h, 5)

heapq.heappush(h, 2)

heapq.heappush(h, 8)

heapq.heappush(h, 4)

print(heapq.heappop(h))

print(heapq.heappop(h))

== >

2

4

2 Data structures are generally based on the ability of a computer to fetch and store data at any place in its memory.

253. Meeting Rooms II