license-key-formatting.js

/**
 * License Key Formatting
 *
 * You are given a license key represented as a string S which consists only alphanumeric character and dashes.
 * The string is separated into N+1 groups by N dashes.
 *
 * Given a number K, we would want to reformat the strings such that each group contains exactly K characters,
 * except for the first group which could be shorter than K, but still must contain at least one character.
 * Furthermore, there must be a dash inserted between two groups and all lowercase letters should be converted to uppercase.
 *
 * Given a non-empty string S and a number K, format the string according to the rules described above.
 *
 * Example 1:
 * Input: S = "5F3Z-2e-9-w", K = 4
 *
 * Output: "5F3Z-2E9W"
 *
 * Explanation: The string S has been split into two parts, each part has 4 characters.
 * Note that the two extra dashes are not needed and can be removed.
 *
 * Example 2:
 * Input: S = "2-5g-3-J", K = 2
 *
 * Output: "2-5G-3J"
 *
 * Explanation: The string S has been split into three parts, each part has 2 characters except the first part
 * as it could be shorter as mentioned above.
 *
 * Note:
 *
 * - The length of string S will not exceed 12,000, and K is a positive integer.
 * - String S consists only of alphanumerical characters (a-z and/or A-Z and/or 0-9) and dashes(-).
 * - String S is non-empty.
 */

/**
 * @param {string} s
 * @param {number} k
 * @return {string}
 */
const licenseKeyFormatting = (s, k) => {
  let key = '';

  for (let c of reverse(s)) {
    if (c !== '-') {
      if (key.length % (k + 1) === k) {
        key += '-';
      }
      key += c.toUpperCase();
    }
  }

  return reverse(key);
};

const reverse = str => [...str].reverse().join('');

export { licenseKeyFormatting };