The Runtime Theory
mediumLeetCode#serialization#length-prefix

Encode and Decode a List of Strings

Design a reversible encoding for a list of arbitrary strings, including empty strings and embedded delimiters.

The Runtime Theory Team25 min read
Solve it

Solving happens on the judge — come back and mark it done

Sample cases

in["lint","code","love","you"]

out["lint","code","love","you"]

in["we","say",":","yes"]

out["we","say",":","yes"]

in[]

out[]

Design a reversible encoding for a list of arbitrary strings, including empty strings and embedded delimiters.

A good solution should

  • State the invariant or decision rule that makes the approach correct.
  • Explain the time and space complexity in terms of the input sizes and required output.
  • Handle empty, minimal, duplicate, and boundary-shaped inputs covered by the contract.

Reasoning prompt

Use an unambiguous framing rule such as length-prefixing. Explain why a delimiter-only format fails when input can contain that delimiter.

Use the linked judge for the canonical problem. The examples above are compact TRT checks; write additional cases before submitting, especially for the boundary that tends to break your chosen invariant.

More practice in this topic

easy · arraysContains Duplicatemedium · arraysGroup Anagramsmedium · arraysLongest Consecutive Sequence

One dispatch a week

The trace behind each problem, the tradeoff that explains it, and one technical dispatch per week — no noise.

One technical dispatch per week. No noise.

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