菜鸟的每日力扣系列——1185. 一周中的第几天

WEEKS = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]
DAYS = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

def dayOfTheWeek(day: int, month: int, year: int) -> str:
    def helper(d, m , y):
        # 2022.1.3 星期一
        res = 1
        # 天的偏移量
        res = (res + d - 3) % 7
        # 年的偏移量
        if y < 2022:
            for i in range(y, 2022):
                res = (res - (366 if not i % 4 and (i % 100 or not i % 400) else 365)) % 7
        else:
            for i in range(2022, y):
                res = (res - (366 if not i % 4 and (i % 100 or not i % 400) else 365)) % 7
        # 月的偏移量
        for i in range(m - 1):
            res = (res + DAYS[i]) % 7
            if i == 1 and not y % 4 and (y % 100 or not y % 400):
                res = (res + 1) % 7
        return res
    return WEEKS[helper(day, month, year)]

day = 31
month = 8
year = 2019
print(dayOfTheWeek(day, month, year))  # Saturday