Suppose `start`

and `end`

are events. Only need to count events, no need to calculate segments overlapping

```
class Solution(object):
def minMeetingRooms(self, intervals):
if len(intervals) == 0:
return 0
ary = []
for i in intervals:
ary.append((i.start, 1))
ary.append((i.end, -1))
ary.sort()
sum, res = 0, 0
for i in ary:
sum += i[1]
res = max(sum, res)
return res
```