271. Encode and Decode Strings

Design encode (list of strings → one string) and decode (string → original list) so that decode(encode(strs)) == strs for any strings.

Write each string as <length>#<string>. The decoder reads digits up to '#', then takes exactly that many characters, so any character (even '#') is safe inside a string.

1function encode(strs: string[]): string {
2  return strs.map((s) => s.length + "#" + s).join("");
3}
4function decode(data: string): string[] {
5  const out: string[] = [];
6  let i = 0;
7  while (i < data.length) {
8    const hash = data.indexOf("#", i);
9    const len = Number(data.slice(i, hash));
10    out.push(data.slice(hash + 1, hash + 1 + len));
11    i = hash + 1 + len;
12  }
13  return out;
14}

strs

neet

co#de

you

encoded

4#neet

Encode "neet" as 4#neet.

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