1071-greatest-common-divisor-of-strings.js

/**
 * 1071. Greatest Common Divisor of Strings
 * https://leetcode.com/problems/greatest-common-divisor-of-strings/
 * Difficulty: Easy
 *
 * For two strings s and t, we say "t divides s" if and only if s = t + t + t + ... + t + t
 * (i.e., t is concatenated with itself one or more times).
 *
 * Given two strings str1 and str2, return the largest string x such that x divides both str1
 * and str2.
 */

/**
 * @param {string} str1
 * @param {string} str2
 * @return {string}
 */
var gcdOfStrings = function(str1, str2) {
  if (str1 + str2 !== str2 + str1) return '';

  for (let i = str2.length; i >= 0; i--) {
    if (str1.length % i === 0 && str2.length % i === 0) {
      return str1.substring(0, i);
    }
  }
};