Date: 2026-06-06
Time: 17:22
license-key-formatting/solution.pyThis file implements LeetCode 482 - License Key Formatting. It's a standalone solution module in a large repository of LeetCode solutions, each following the same directory structure (solution.py, testsolution.py, plan.md, review.md). Its single responsibility is exposing the licensekey_formatting function.
licensekeyformatting(s: str, k: int) -> str — the sole public function. Takes a license key string containing alphanumeric characters and dashes, plus a group size k, and returns a reformatted key where:
k, separated by dashesk characters (the remainder)The algorithm is three steps:
1. Normalize (line 13): s.replace("-", "").upper() strips all dashes and uppercases in one pass, producing a clean alphanumeric string.
2. Compute first group size (line 14): len(cleaned) % k determines how many characters belong in the potentially-short first group. If first == 0, there is no short group — all groups are exactly k.
3. Build groups (lines 15–18): Conditionally appends the short first group, then iterates from offset first in steps of k, slicing exact-size groups. This loop correctly handles the first == 0 case because range(0, n, k) starts at index 0.
4. Join (line 19): Dash-separates all groups.
replace + upper), then rebuilds it from scratch. This is the idiomatic approach for reformatting problems — avoids edge cases around existing group boundaries.len % k upfront and handling the short prefix separately, then iterating uniformly for the rest. This is the standard pattern for "all groups size k except possibly the first."Imports: None — pure Python, no standard library or third-party imports.
Imported by: The testsolution.py files listed in the "Imported By" section appear to be a cross-reference artifact from the tooling rather than actual imports of this function. The real consumer is license-key-formatting/testsolution.py.
k characters.k characters (inclusive), unless the input is empty.parts is never padded with empty strings — first == 0 skips the first append, and the loop produces no empty slices since cleaned[i:i+k] with i < len(cleaned) is always non-empty).cleaned is empty (input was all dashes or empty), parts stays empty and the result is "".None. The function assumes valid inputs per the LeetCode contract: s contains only alphanumeric characters and dashes, and k >= 1. Passing k=0 would cause a ZeroDivisionError on line 14 and an infinite loop in range. This is acceptable — LeetCode guarantees 1 <= k <= 10^4.
license-key-formatting/test_solution.py — See the test cases to understand edge cases (all dashes, single character, exact multiples of k)license-key-formatting/review.md — Code review notes that may cover alternative approaches or performance observationsstrip-then-partition-pattern — This normalize-then-rebuild approach recurs across string reformatting problems like reformat-phone-number and divide-a-string-into-groups-of-size-kdivide-a-string-into-groups-of-size-k/solution.py — Similar grouping logic but with a fill character for the last group instead of a short first groupreformat-phone-number/solution.py — Another string reformatting problem that strips then repartitionslicense-key-first-group-remainder — The first group size equals len(cleaned) % k; all subsequent groups are exactly k characterslicense-key-no-imports — The solution uses no imports — it relies entirely on str.replace, str.upper, and slicinglicense-key-empty-input-safe — An input of all dashes (or empty string) produces an empty string without error, because the loop range is empty and parts stays []license-key-uppercase-guarantee — The output never contains lowercase letters because .upper() is applied to the entire cleaned string before grouping