Counting Sundays

https://projecteuler.net/problem=19

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)?

简单化处理，直接从1901年往上加日期，而不是写一个函数，直接计算时间，那样有点麻烦，虽然比较通用，等问题难了的话，再写那个函数吧。

def numMonth():
    count = 0
    days = 366 - 31  #1900年12月1号
    for i in range(1901,2001):
        for j in range(1,13):
            days += getDays(i,j - 1)  #把上个月的天数加上去
            if isSunday(days):
                count += 1
                print(i,j)
    return count

def getDays(year,month):
    if month in (0,1,3,5,7,8,10): #0代表的是上一年的12月份
        return 31
    elif month in (4,6,9,11):
        return 30
    elif year % 400 == 0:
        return 29
    elif year % 4 == 0:
        return 29
    else:
        return 28

def isSunday(days):
    if days % 7 == 0:
        return True
    else:
        return False

print(numMonth())