BOJ - 11000 - 강의실 배정

import sys
import heapq

def solution():
    cnt = 1
    N = int(sys.stdin.readline())
    pq, rooms = [], []
    for _ in range(N):
        [a, b] = [int(e) for e in sys.stdin.readline().split()]
        heapq.heappush(pq, (a, b))

    heapq.heappush(rooms, heapq.heappop(pq)[1])
    while pq:
        curr = heapq.heappop(pq)
        if curr[0] < rooms[0]:
            cnt += 1
        else:
            heapq.heappop(rooms)
        heapq.heappush(rooms, curr[1])
    print(cnt)

solution()

https://www.acmicpc.net/problem/11000