Looks easy until you start thinking about duplicates and how to enumerate efficiently.
Start by clarifying the problem: confirm whether substrings are contiguous, whether uniqueness is case-sensitive, and the expected output format. Then propose an efficient algorithm using a set to collect all substrings, analyzing time and space complexity. Discuss trade-offs between brute-force and optimized approaches, and consider edge cases.
Pro tip: Mention that the number of substrings is O(n^2), so the output size itself is quadratic; this shows you understand the problem's inherent complexity and can set realistic expectations. Also, briefly discuss how to handle very large strings or memory constraints, demonstrating practical engineering thinking.
Ask whether substrings must be contiguous, if uniqueness is case-sensitive, and what output format is expected (e.g., list, set). Confirm constraints on string length and character set.
Explain that you can generate all substrings using two nested loops and insert them into a set to remove duplicates. State time complexity O(n^3) if using string slicing, or O(n^2) with efficient hashing.
Propose using a suffix automaton or suffix trie to generate unique substrings in O(n) or O(n^2) time, depending on implementation. Discuss trade-offs in complexity and implementation difficulty.
Calculate time and space complexity for the chosen approach. Discuss edge cases: empty string, single character, all identical characters, and very long strings.
Mention that the number of unique substrings can be O(n^2), so output size may be large. Suggest streaming or limiting output if needed, and consider memory usage.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.