pq.py

from heapq import heappush, heappop

schedule = [(1, 3), (2, 5), (4, 5)]

def required_rooms(schedule):
  h = []
  for start, end in schedule:
    if len(h) > 0 and h[0] <= start:
      heappop(h)
    heappush(h, end)
  return len(h)