The tricky part is that strings can have literally any character, so you can't just pick a delimiter and call it a day.
Start by clarifying constraints (e.g., delimiter choice, empty strings, Unicode) and then propose a length-prefixed encoding where each string is prefixed with its length and a delimiter. Implement serialize by concatenating length, delimiter, and string for each element, and deserialize by parsing the length, skipping the delimiter, and reading exactly that many characters. Discuss trade-offs between this approach and alternatives like escaping or JSON, emphasizing efficiency and correctness.
Pro tip: Mention that length-prefixing is O(n) time and space and handles all characters without escaping, but note that the length prefix itself must be delimited unambiguously (e.g., using a non-digit delimiter). This shows you've considered edge cases like strings containing the delimiter.
Ask about input size, character set (ASCII/Unicode), empty strings, and whether the serialized format needs to be human-readable. This ensures you design an appropriate solution.
Propose length-prefixed encoding: for each string, write its length, a delimiter (e.g., '#'), then the string itself. Explain why this avoids ambiguity even if strings contain the delimiter.
Iterate through the list, and for each string, append its length, the delimiter, and the string to a result builder. Return the concatenated string.
Parse the serialized string by reading digits until the delimiter to get the length, then skip the delimiter and read exactly that many characters as the next string. Repeat until the end.
State that both functions run in O(n) time and space, where n is the total number of characters. Discuss edge cases: empty list, empty strings, strings with delimiters, and large lengths.
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