問題
Return the number of days in month of year in the Gregorian calendar. February has 29 days in a leap year: years divisible by 4, except those divisible by 100 unless also divisible by 400. A helper function is_leap(year) keeps the code tidy.
Implement days_in_month(year, month).
Input
year: The year. month: The month, 1 (January) to 12 (December).
Output
Return the number of days.
制約
1 ≤ year ≤ 9,999; 1 ≤ month ≤ 12
例
例 1
入力：
year = 2024
month = 2
期待される出力：
expected = 29入力：
long long year = 2024;
long long month = 2;
期待される出力：
long long expected = 29;入力：
long year = 2024;
long month = 2;
期待される出力：
long expected = 29;解説
2024 is divisible by 4 and not by 100, so it is a leap year: 29 days.
例 2
入力：
year = 1900
month = 2
期待される出力：
expected = 28入力：
long long year = 1900;
long long month = 2;
期待される出力：
long long expected = 28;入力：
long year = 1900;
long month = 2;
期待される出力：
long expected = 28;解説
1900 is divisible by 100 but not 400, so it is not a leap year: 28 days.
参考資料
この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。