Variant of Longest Substring Without Repeating Characters (string version, multiple follow-ups)

Problem Given a string s, implement a function to compute the length (or return the substring itself, as required) of the longest contiguous substring that satisfies certain uniqueness constraints. This is a variant of LeetCode 3 and came with multiple follow-ups in the interview. Base version Find the longest substring where all characters are distinct. Variants / follow-ups (as described verbally) Generalize the constraint from “no repeated characters” to “unique name/identifier” (an array-version rephrased into a string-version). Another follow-up mentioned: find the longest contiguous subarray/substring with unique names. Note: The original interview note does not provide the full formal statement of each variant, so this summarizes the question family as “longest window under a uniqueness constraint”. I/O Input: a string s Output: length of the longest valid substring (or the substring itself) Constraints 1 <= len(s) <= 2e5 (typical interview scale; aim for O(n) or near O(n)) Examples Input: abcabcbb -> Output: 3 Input: bbbbb -> Output: 1 Input: pwwkew -> Output: 3 Sample tests (5) abcabcbb -> 3 bbbbb -> 1 pwwkew -> 3 (empty string) -> 0 dvdf -> 3 Example Input abcabcbb Output 3