#3167 - Better Compression of String

Problem Description

You are given a string compressed representing a compressed version of a string. The format is a character followed by its frequency. For example, "a3b1a1c2" is a compressed version of the string "aaabacc".

We seek a better compression with the following conditions:

Each character should appear only once in the compressed version.
The characters should be in alphabetical order.

Return the better compression of compressed.

Note: In the better version of compression, the order of letters may change, which is acceptable.

Solution

/**
 * @param {string} compressed
 * @return {string}
 */
var betterCompression = function(compressed) {
  const map = new Map();
  let i = 0;

  while (i < compressed.length) {
    const char = compressed[i];
    i++;

    let frequency = '';
    while (i < compressed.length && !isNaN(compressed[i])) {
      frequency += compressed[i];
      i++;
    }

    const count = parseInt(frequency);
    map.set(char, (map.get(char) || 0) + count);
  }

  const sortedChars = [...map.keys()].sort();
  const result = sortedChars.map(char => char + map.get(char)).join('');

  return result;
};