number-of-days-in-a-month.py

# Time:  O(1)
# Space: O(1)

class Solution(object):
    def numberOfDays(self, Y, M):
        """
        :type Y: int
        :type M: int
        :rtype: int
        """
        leap = 1 if ((Y % 4 == 0) and (Y % 100 != 0)) or (Y % 400 == 0) else 0
        return (28+leap if (M == 2) else 31-(M-1)%7%2)