#1309 - Decrypt String from Alphabet to Integer Mapping

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Problem Description

Given a string s formed by digits ('0' - '9') and '#' .

We want to map s to English lowercase characters as follows:

Characters ('a' to 'i') are represented by ('1' to '9') respectively.
Characters ('j' to 'z') are represented by ('10#' to '26#') respectively.

Return the string formed after mapping.

It's guaranteed that a unique mapping will always exist.

Solution

/**
 * @param {string} s
 * @return {string}
 */
var freqAlphabets = function(s) {
  return s.replace(/\d{2}#|\d/g, match => {
    return String.fromCharCode('a'.charCodeAt() + parseInt(match, 10) - 1);
  });
};