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Encode and Decode Strings

medium
NeetCode 150stringsdesign

Problem

Design an encoder that serializes a list of arbitrary strings into one string, and a decoder that recovers the original list. The strings may contain any characters, including your delimiters.

Examples

Input: ["neet", "code", "love", "you"]
Output: decode(encode(input)) == input
Round-tripping must reproduce the original list exactly.
Input: ["", "a#b"]
Output: decode(encode(input)) == input
Empty strings and embedded delimiters must survive.

Constraints

  • • 0 <= list length <= 200
  • • Strings may contain any Unicode characters
Hints(tap to reveal)
  • 1. A naive separator fails when the data contains it.
  • 2. Length-prefixing each chunk removes ambiguity.
Optimal approach(spoiler)
  1. Encode each string as its length, a separator character, then the raw string.
  2. Concatenate these length-prefixed chunks.
  3. To decode, read the integer length up to the separator.
  4. Slice out exactly that many characters, then repeat from the next chunk.
  5. Length-prefixing is robust to any content in the payload.

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