Date: 2026-06-06
Time: 18:16
number-of-days-in-a-month/solution.pyThis file solves LeetCode 1118 — Number of Days in a Month. It provides a single function that, given a year and month, returns how many days that month has. The problem's core challenge is handling February correctly across leap years.
numberofdays(year: int, month: int) -> int — The sole function. Takes a Gregorian year (1583–2100) and month (1–12), returns the day count (28, 29, 30, or 31).
days list — A lookup table of base day counts for months 1–12, with February defaulting to 28. Indexed by month - 1 to convert from 1-based month to 0-based list index.
Lookup table + special case: The solution avoids a chain of if/elif by storing the common case in a list and only branching for the one irregular month (February in a leap year). This is the standard idiom for this problem.
Early return: The leap-year check short-circuits before the general lookup, so February in a leap year never reaches the days[month - 1] fallback.
Imports: None — pure arithmetic and a list literal.
Imported by: The testsolution.py in this same directory. The "Imported By" list in the prompt is misleading — those hundreds of test files each import their *own* solution.py, not this one. The only real consumer is number-of-days-in-a-month/testsolution.py.
1. Build the 12-element days list (February = 28).
2. Check if month == 2 and the year satisfies the Gregorian leap-year rule:
3. If both conditions hold, return 29.
4. Otherwise, return days[month - 1].
The leap-year predicate (year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)) is the textbook Gregorian rule. The parenthesization is correct: %100 != 0 handles the century exception, %400 == 0 handles the 400-year re-exception.
month is in [1, 12] and year is in the problem's stated range (1583–2100). No validation is performed; out-of-range months will raise IndexError from the list lookup.days list is reconstructed on every call (local variable, not module-level constant). Functionally irrelevant for correctness, minor for performance.None. Invalid inputs (month 0, month 13, negative years) are not guarded. A month of 0 would return days[-1] (31 — December, via Python's negative indexing), which is silently wrong rather than an error. Month 13 would raise IndexError.