sol1.py

"""
Counting Sundays
Problem 19

You are given the following information, but you may prefer to do some research
for yourself.

1 Jan 1900 was a Monday.
Thirty days has September,
April, June and November.
All the rest have thirty-one,
Saving February alone,
Which has twenty-eight, rain or shine.
And on leap years, twenty-nine.

A leap year occurs on any year evenly divisible by 4, but not on a century
unless it is divisible by 400.

How many Sundays fell on the first of the month during the twentieth century
(1 Jan 1901 to 31 Dec 2000)?
"""


defsolution():
"""Returns the number of mondays that fall on the first of the month during
 the twentieth century (1 Jan 1901 to 31 Dec 2000)?

 >>> solution()
 171
 """
days_per_month= [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

day=6
month=1
year=1901

sundays=0

whileyear<2001:
day+=7

if (year%4==0andyear%100!=0) or (year%400==0):
ifday>days_per_month[month-1] andmonth!=2:
month+=1
day=day-days_per_month[month-2]
elifday>29andmonth==2:
month+=1
day=day-29
elifday>days_per_month[month-1]:
month+=1
day=day-days_per_month[month-2]

ifmonth>12:
year+=1
month=1

ifyear<2001andday==1:
sundays+=1
returnsundays


if__name__=="__main__":
print(solution())