271-string-encode-and-decode

271. Encode and Decode Strings (Medium) (https://neetcode.io/problems/string-encode-and-decode/question?list=neetcode150)

Design an algorithm to encode a list of strings to a single string. The encoded string is then decoded back to the original list of strings. Constraints / Notes: - The input strings may contain any characters.

• You must ensure the encoding is reversible without ambiguity.

class Codec {
  constructor() {
 
  }
 
  encode(strs: string[]): string {
    // [length] + "#" + [data]
    let encoded_string = ''
    for (const word of strs) {
      encoded_string += word.length + '#' + word
    }
    return encoded_string
  }
 
  decode(s: string): string[] {
    const decoded: string[] = []
    let idx = 0
 
    while (idx < s.length) {
      let length: string = ''
      while (idx < s.length && s[idx] !== '#') {
        length += s[idx]
        idx += 1
      }
      const numLength = Number(length)
      decoded.push(s.slice(idx + 1, idx + numLength + 1))
      idx += numLength + 1
    }
    return decoded
  }
}
 
 
// Local check:
const codec = new Codec()
 
console.log(codec.decode(codec.encode(["hello", "world"])))
console.log(codec.decode(codec.encode(["lint", "code", "love", "you"])))
console.log(codec.decode(codec.encode([""])))

Example 1:
 
    Input: ["hello","world"]
    Output: ["hello","world"]
    Explanation:
      After encoding and then decoding, we get the original array back.
 
  Example 2:
 
    Input: ["lint","code","love","you"]
    Output: ["lint","code","love","you"]

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