/
19.py
50 lines (40 loc) · 1.25 KB
/
19.py
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# 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)?
# Answer: 171
def is_leap_year(year):
if year % 4 == 0 and year % 100 != 0 or year % 400 == 0:
return True
return False
def days_of_month(year, month):
if month in (1, 3, 5, 7, 8, 10, 12):
return 31
elif month == 2:
if is_leap_year(year):
return 29
else:
return 28
else:
return 30
def main():
sundays = 0
year, month, week = 1901, 0, 2
while year <= 2000:
week = (week + days_of_month(year, month+1)) % 7
if week == 0:
sundays += 1
month = (month + 1) % 12
if month == 0:
year = year + 1
print(sundays)
if __name__ == '__main__':
main()