Q30: Encode and Decode Strings

Design an algorithm to encode a list of strings to a single string and decode that single string back to the original list of strings.

Length-Prefix String Serialization

function encode(strs) {
  return strs.map(s => `${s.length}#${s}`).join('');
}

function decode(str) {
  const result = [];
  let i = 0;
  while (i < str.length) {
    let j = i;
    while (str[j] !== '#') j++;
    const length = parseInt(str.slice(i, j), 10);
    i = j + 1;
    result.push(str.slice(i, i + length));
    i += length;
  }
  return result;
}

const encoded = encode(['lint', 'code', 'love', 'you']);
console.log(encoded); // '4#lint4#code4#love3#you'
console.log(decode(encoded)); // ['lint', 'code', 'love', 'you']

💡 Encoding formats strings as length#string. Decoding locates #, parses integer length, and slices exact character byte segments safely.

Key Takeaways

Prefix each string with its character length followed by a delimiter (e.g. 4#code).
Avoids parsing errors caused by delimiter characters appearing inside original string content.

Knowledge Check

Why is length-prefixing preferable to simple character delimiting (e.g. comma separation)?

Q30: Encode and Decode Strings

STAY UPDATED WITH BYTES!