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Google·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
May 2026

Summary

Google SWE coding round, one question about serializing and deserializing a list of strings. Pretty focused session, no fluff.

Questions Asked (1)

Q1

Write functions to serialize and deserialize a list of strings.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

Looks easy until you start thinking about edge cases.

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AI HintsAI Generated

Suggested Approach

Clarify constraints (e.g., delimiter choice, escaping, empty strings, Unicode) and then design a length-prefixed encoding to avoid ambiguity. Implement serialize by concatenating length and string with a delimiter, and deserialize by parsing lengths and extracting substrings. Discuss trade-offs between simplicity and robustness.

Pro tip: Mention that length-prefixing is more robust than delimiter-based encoding because it handles arbitrary strings including delimiters and empty strings. Also, consider using a single delimiter like '#' after the length to simplify parsing.

1. Clarify Requirements and Constraints

Ask about input size, character set, whether strings can contain any characters, and if the serialized format needs to be human-readable. This determines the encoding strategy.

2. Choose an Encoding Scheme

Decide between delimiter-based (with escaping) or length-prefixed encoding. Length-prefixed is generally safer and simpler to parse.

3. Implement Serialize

For each string, append its length, a delimiter (e.g., '#'), and the string itself. Concatenate all into a single string.

4. Implement Deserialize

Parse the serialized string by reading digits until the delimiter to get the length, then extract that many characters as the next string. Repeat until the end.

5. Test and Discuss Edge Cases

Test with empty list, empty strings, strings containing delimiters, and Unicode characters. Discuss time/space complexity and potential improvements.

Key Points to Mention

  • Length-prefixed encoding avoids ambiguity with delimiters and handles empty strings.
  • Use a delimiter like '#' after the length to separate length from content.
  • Time complexity: O(n) for both serialize and deserialize, where n is total characters.
  • Space complexity: O(n) for the serialized string.
  • Edge cases: empty list, empty strings, strings with special characters, Unicode.
  • Trade-offs: simplicity vs. robustness; escaping vs. length-prefixing.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.