Find longest unique substring
Company: Lowe's
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
Given a string s, find the length and one example of the longest substring of s that contains no repeated characters. If multiple answers exist, return any valid one. Explain your algorithm, prove its correctness at a high level, analyze time and space complexity, and discuss edge cases (e.g., empty string, all identical characters, presence of Unicode code points).
Quick Answer: This question evaluates proficiency in string algorithms, character-encoding awareness, and the ability to reason about auxiliary data structures for tracking uniqueness and algorithmic complexity.