0893-groups-of-special-equivalent-strings.js

/**
 * 893. Groups of Special-Equivalent Strings
 * https://leetcode.com/problems/groups-of-special-equivalent-strings/
 * Difficulty: Medium
 *
 * You are given an array of strings of the same length words.
 *
 * In one move, you can swap any two even indexed characters or any two odd indexed characters of
 * a string words[i].
 *
 * Two strings words[i] and words[j] are special-equivalent if after any number of moves,
 * words[i] == words[j].
 * - For example, words[i] = "zzxy" and words[j] = "xyzz" are special-equivalent because we may
 *   make the moves "zzxy" -> "xzzy" -> "xyzz".
 *
 * A group of special-equivalent strings from words is a non-empty subset of words such that:
 * - Every pair of strings in the group are special equivalent, and
 * - The group is the largest size possible (i.e., there is not a string words[i] not in the
 *   group such that words[i] is special-equivalent to every string in the group).
 *
 * Return the number of groups of special-equivalent strings from words.
 */

/**
 * @param {string[]} words
 * @return {number}
 */
var numSpecialEquivGroups = function(words) {
  return new Set(words.map(normalizeWord)).size;

  function normalizeWord(word) {
    const evenChars = [];
    const oddChars = [];
    for (let i = 0; i < word.length; i++) {
      if (i % 2 === 0) evenChars.push(word[i]);
      else oddChars.push(word[i]);
    }
    return `${evenChars.sort().join('')}-${oddChars.sort().join('')}`;
  }
};