解决问题19

Signed-off-by: SidneyZhang <zly@lyzhang.me>

solutions/0019.CountingSundays/euler_19.py

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+"""
+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)?
+"""
+
+import time
+
+
+def timer(func):
+    def wrapper(*args, **kwargs):
+        start_time = time.time()
+        result = func(*args, **kwargs)
+        end_time = time.time()
+        print(f"Execution time: {end_time - start_time} seconds")
+        return result
+
+    return wrapper
+
+
+def is_leap_year(year: int) -> bool:
+    return (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
+
+
+def days_in_years(years: list[int]) -> int:
+    leapyears = [year for year in years if is_leap_year(year)]
+    return sum([366 if year in leapyears else 365 for year in years])
+
+
+def count_sundays(start_year: int | str, end_year: int | str) -> int:
+    start_year = int(start_year) if isinstance(start_year, str) else start_year
+    end_year = int(end_year) if isinstance(end_year, str) else end_year
+    if start_year < 1900 or start_year > end_year:
+        raise ValueError(f"Invalid year range {start_year} to {end_year}")
+    last_days = days_in_years(list(range(1900, start_year)))
+    year_list = list(range(start_year, end_year + 1))
+    days = days_in_years(year_list) + (last_days % 7)
+    sundays = days // 7
+    return sundays
+
+
+def days_month(year: int, month: int) -> int:
+    if month in [1, 3, 5, 7, 8, 10, 12]:
+        return 31
+    elif month in [4, 6, 9, 11]:
+        return 30
+    elif month == 2:
+        return 29 if is_leap_year(year) else 28
+    else:
+        raise ValueError(f"Invalid month {month}")
+
+
+def days_sunday_month(start_year: int, end_year: int) -> int:
+    count = 0
+    outday = days_in_years(list(range(1900, start_year))) % 7
+    for year in range(start_year, end_year + 1):
+        for month in range(1, 13):
+            if outday == 6:
+                count += 1
+            outday = (outday + days_month(year, month)) % 7
+    return count
+
+
+@timer
+def main() -> None:
+    print(f"Number of Sundays between 1901 and 2000: {count_sundays(1901, 2000)}")
+
+
+@timer
+def main_first_day() -> None:
+    print(
+        f"Number of Sundays on the first of the month between 1901 and 2000: {days_sunday_month(1901, 2000)}"
+    )
+
+
+if __name__ == "__main__":
+    main()
+    main_first_day()