Date: 2026-06-06
Time: 19:17
strong-password-checker-ii/solution.pyThis file implements LeetCode problem 2299 ("Strong Password Checker II"). It validates whether a password meets all six strength criteria defined by the problem. It's a standalone solution module — one of hundreds in this repo, each solving a single LeetCode problem.
Solution.strongpasswordchecker_ii(self, password: str) -> bool — The sole public method. Returns True only if password satisfies all six rules simultaneously:
1. Length >= 8
2. Contains at least one lowercase letter
3. Contains at least one uppercase letter
4. Contains at least one digit
5. Contains at least one special character from !@#$%^&*()-+ (and space)
6. No two adjacent characters are the same
The method uses an early-return for the length check, then does a single-pass scan over the string:
1. Length gate (line 11): Rejects passwords shorter than 8 characters immediately.
2. Single loop (lines 16–23): Iterates with enumerate to get both index and character. For each character:
i > 0 and current char equals previous, returns False immediately. This is the only rule that triggers an early exit mid-loop.elif chain for lowercase/uppercase/digit, plus a separate if for special characters. The elif means a special character like ! won't accidentally set haslower/hasupper/has_digit — but the special-char check is a standalone if, so it runs regardless of the elif outcome.3. Final conjunction (line 26): All four boolean flags must be True.
False and are flipped to True as evidence is found. This is the standard "checklist" idiom — you can't short-circuit because you need to see every character for the adjacent-duplicate rule anyway.specials = set("!@#$%^&*()-+ ") gives O(1) lookup per character. The set is rebuilt on every call (it's inside the method), but for a password-length string this is negligible.False immediately rather than setting a flag. This is valid because a single violation is sufficient to fail.Imports: None — pure Python, no standard library or third-party imports.
Imported by: The strong-password-checker-ii/test_solution.py file imports this module directly. The large "Imported By" list in the prompt is misleading — those are test files for *other* problems that happen to share a common test harness or import pattern across the repo, not actual consumers of this solution's logic.
elif chain (lines 19–22) is mutually exclusive for lowercase/uppercase/digit classification: a character can only set one of those three flags. This is safe because no character is simultaneously lowercase, uppercase, and a digit.elif chain. A space character, for example, is not lowercase/uppercase/digit, so it falls through the elif without setting any flag — but the standalone if ch in specials still catches it. This separation is correct.i > 0 guards against out-of-bounds access to password[i - 1] when i == 0.None. The method is a pure function with no exceptions, no I/O, and no edge cases that could raise. Empty strings are handled correctly (fail the length check). The method always returns a bool.
strong-password-checker-ii/test_solution.py — See what edge cases the tests cover (empty string, exactly 8 chars, all-same-char, missing one category)strong-password-checker-ii/review.md — Read the code review notes for this solution to see if any issues were flaggedsingle-pass-validation-pattern — This flag-accumulation-in-one-loop pattern recurs across many validation problems in the repostrong-password-checker-ii/solution.py:strongpasswordchecker_ii — Compare with the harder variant (Strong Password Checker I, problem 420), which requires computing minimum *edits* to make a password strongspecial-char-check-independent-of-elif — The special character check uses a standalone if (not elif), so characters that are neither lower/upper/digit can still be recognized as specialadjacent-duplicate-is-early-exit — A single pair of adjacent identical characters causes immediate False return, unlike the category flags which are accumulatedno-short-circuit-on-category-flags — Even after all four category flags are True, the loop continues to completion because it must still check every adjacent pair for duplicatesspecials-set-includes-space — The special characters set includes the space character, which is part of the LeetCode problem's specification