#271 - Encode and Decode Strings

Problem Description

Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.

Machine 1 (sender) has the function: string encode(vector<string> strs) { // ... your code return encoded_string; } Machine 2 (receiver) has the function: vector<string> decode(string s) { //... your code return strs; } So Machine 1 does: string encoded_string = encode(strs); and Machine 2 does: vector<string> strs2 = decode(encoded_string); strs2 in Machine 2 should be the same as strs in Machine 1.

Implement the encode and decode methods.

You are not allowed to solve the problem using any serialize methods (such as eval).

Solution

/**
 * Encodes a list of strings to a single string.
 *
 * @param {string[]} strs
 * @return {string}
 */
var encode = function(strs) {
  return strs.map(str => `${str.length}:${str}`).join('');
};

/**
 * Decodes a single string to a list of strings.
 *
 * @param {string} s
 * @return {string[]}
 */
var decode = function(s) {
  const result = [];
  let i = 0;

  while (i < s.length) {
    const colon = s.indexOf(':', i);
    const len = parseInt(s.slice(i, colon));
    result.push(s.slice(colon + 1, colon + 1 + len));
    i = colon + 1 + len;
  }

  return result;
};