The core logic wasn't too bad to reason through but I fumbled the edge cases.
Clarify the input format and assumptions, then propose a single-pass line-by-line parser that tracks the current User-agent section and collects Disallow URLs into a set for uniqueness. Discuss edge cases like multiple User-agent lines, comments, whitespace, and case sensitivity, and analyze time/space complexity.
Pro tip: Mention that you would confirm whether 'User-agent:' lines can appear multiple times before a single set of rules, as this affects whether you need to merge or reset the current section. Also note that using a set gives O(1) average insertion and naturally handles duplicates.
Ask about the exact format: are there comments, blank lines, or inline comments? Can a section have multiple User-agent lines? Are URLs case-sensitive as stated? Confirm that 'Disallow:' values are the full URL paths.
Propose a single-pass approach: iterate through each line, detect 'User-agent:' to start a new section, and when in a section, detect 'Disallow:' to extract the URL. Use a set to store unique URLs.
Address trimming whitespace, ignoring comments (lines starting with #), handling empty Disallow values, and ensuring case sensitivity. Consider if multiple User-agent lines share the same rules (common in robots.txt).
State that time complexity is O(n) where n is total characters or lines, and space is O(u) for unique URLs. Discuss using a set vs list for deduplication, and whether streaming is possible.
Walk through a small example to verify correctness, including duplicate Disallow entries and multiple sections. Mention potential pitfalls like case sensitivity and leading/trailing spaces.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.