My first instinct was to just iterate over the dict keys and do a find-replace for each one, which they immediately pushed back on.
Clarify the token format and edge cases, then propose a single-pass scan using an index pointer that checks for a semicolon, extracts the key up to the next colon, and looks it up in the dictionary. If found, append the replacement; otherwise, append the original token. This avoids re-scanning or checking every key at each semicolon.
Pro tip: Emphasize that the dictionary lookup is O(1) on average, making the overall solution O(n) time and O(m) space for the output, and mention that you'd handle edge cases like malformed tokens or overlapping patterns by defining clear rules upfront.
Ask about token format (e.g., can keys contain semicolons or colons?), behavior for malformed tokens, and whether replacements can introduce new tokens. Confirm that unmatched tokens remain unchanged.
Use a pointer to scan the string. When a semicolon is found, find the next colon, extract the key, and check the dictionary. Append the replacement or the original substring accordingly, then continue after the token.
Explain that the scan is O(n) time with O(1) dictionary lookups, and O(n) space for the output. Contrast with a naive approach that checks every key at each semicolon, which would be O(n*k).
Walk through examples: no tokens, unmatched keys, adjacent tokens, tokens at start/end. Discuss how to handle malformed tokens (e.g., missing colon) by treating them as literal text.
Write clean code with clear variable names, using a StringBuilder for efficiency. Test with provided examples and additional edge cases to ensure correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.