Date: 2026-06-06
Time: 18:24
number-of-valid-clock-times/solution.pyThis file solves LeetCode 2437 — Number of Valid Clock Times. Given a time string like "?5:00" where ? represents an unknown digit, it counts how many valid 24-hour clock times can be formed by replacing every ? with a digit 0–9. The file is self-contained: it defines the solution function and its unit tests in one module.
countvalidtimes(time: str) -> int — The core solver. Takes a 5-character string in "hh:mm" format and returns the count of valid replacements for all ? characters.
matches(pattern: str, value: str) -> bool — Inner helper that checks whether a two-character pattern (e.g. "?5") matches a candidate value (e.g. "05"). A ? in the pattern matches any digit; a literal digit must match exactly.
TestCountValidTimes — 10 test cases covering full wildcards, no wildcards, boundary hours (23:59), and single-position wildcards for each of the four digit positions.
Independent-dimension enumeration. The key insight is that hours and minutes are independent — knowing which hours match the hour pattern tells you nothing about which minutes match the minute pattern. So the total is simply hours * minutes. This avoids enumerating all 1440 possibilities.
Brute-force-with-filter over a small domain. Rather than building a case table for each ? position (e.g., "if tens digit is ? and ones digit is 3, tens can be 0, 1, or 2"), the code iterates over all 24 hours and all 60 minutes, formatting each as a two-digit string and testing against the pattern. The domain is small enough (24 + 60 = 84 iterations) that this is effectively free.
Pattern matching via zip. The matches helper pairs pattern characters with candidate characters and short-circuits on mismatch. This is idiomatic Python for character-level string comparison with wildcards.
Imports: Only unittest from the standard library. No external dependencies.
Imported by: The test_solution.py in this same directory, plus the file's test class is structured to run standalone via unittest.main(). The massive "Imported By" list in the repo context appears to be a tooling artifact — those other test files don't actually import this module; they share the same structural pattern.
1. Split the input at the colon: hpattern = time[:2], mpattern = time[3:5].
2. Count matching hours: iterate range(24), format each as f"{h:02d}", check against h_pattern via matches.
3. Count matching minutes: iterate range(60), format each as f"{m:02d}", check against m_pattern via matches.
4. Return the product hours * minutes.
time is exactly 5 characters in the shape "XX:XX" where each X is a digit or ?. No validation is performed.time[:2] and time[3:5]), and hours/minutes are treated as fully independent dimensions.None. The function trusts its input. Malformed strings (wrong length, invalid characters, missing colon) would silently produce incorrect results rather than raising exceptions. This is typical for LeetCode solutions where input constraints are guaranteed by the problem.