main.js

// URL: https://leetcode.com/problems/scramble-string/

const _isScramble = function (s1, s2, trackMap) {
  if (s1.length !== s2.length) return false;
  if (s1 === s2) return true;
  if (s1.length === 0 || s2.length === 0) return true;
  const trackKey = s1 + s2;
  if (trackKey in trackMap) return !!trackMap[trackKey];

  let result = false;
  let xorFW = 0;
  let xorBW = 0;

  for (
    var i = 0, j = s1.length - 1, iPlus = 1;
    i < s1.length - 1;
    i++, j--, iPlus++
  ) {
    xorFW ^= s1.charCodeAt(i) ^ s2.charCodeAt(i);
    xorBW ^= s1.charCodeAt(i) ^ s2.charCodeAt(j);

    if (
      xorFW === 0 &&
      _isScramble(s1.substring(0, iPlus), s2.substring(0, iPlus), trackMap) &&
      _isScramble(s1.substring(iPlus), s2.substring(iPlus), trackMap)
    ) {
      result = true;
      break;
    }

    if (
      xorBW === 0 &&
      _isScramble(
        s1.substring(0, iPlus),
        s2.substring(s1.length - iPlus),
        trackMap
      ) &&
      _isScramble(
        s1.substring(iPlus),
        s2.substring(0, s1.length - iPlus),
        trackMap
      )
    ) {
      result = true;
      break;
    }
  }

  trackMap[trackKey] = result;
  trackMap[s2 + s1] = result;
  return result;
};

/**
 * @param {string} s1
 * @param {string} s2
 * @return {boolean}
 */
const isScramble = function (s1, s2) {
  return _isScramble(s1, s2, {});
};