finding max number of meeting rooms

gistfile1.py

meetings_sample = [(0, 30), (60, 90), (20, 65)]
[(0,True),(30,False),(60,True),(90,False),(20,True),(65,False)]

def count_rooms(meeting_events):
    meeting_events.sort(lambda x,y: x[0]<y[0]) # O(nlogn), need to add sorting here so that False is first
    # not sure if that sort is left associative or right 
    # associative
    ongoing_meetings = [] # pretend stack
    max_num_meetings = 0 # initialize
    stack_size = 0
    for time, is_start in meeting_events
        if (is_start): 
            ongoing_meetings.append((time))
            stack_size += 1
        else:
            ongoing_meetings.pop()
            stack_size -= 1
        max_num_meetings = max(max_num_meetings, stack_size)
    return max_num_meetings

# return True if overlap in meetings
def has_overlap(meetings):
    meetings.sort(key= lambda x: x[0]) # O(nlogn)
    prev_end_time = -1
    for start, end in meetings:
        if start < prev_end_time:
            return true 
        else:
            prev_end_time = end
    return false

I think the count_rooms() at line 38 might be more efficient due to O(1) additional space, since it doesnt have stack?