ScrambleStrings.js

// Problem Statement and Explanation: https://leetcode.com/problems/scramble-string/

/**
 * Given two strings s1 and s2 of the same length, return true if s2 is a scrambled string of s1, otherwise, return false.
 * @param {string} s1
 * @param {string} s2
 * @return {boolean}
 */

const isScramble = (s1, s2) => {
 return helper({}, s1, s2)
}

const helper = function (dp, s1, s2) {
 const map = {}

 if (dp[s1 + s2] !== undefined) return dp[s1 + s2]
 if (s1 === s2) return true

 for (let j = 0; j < s1.length; j++) {
 if (map[s1[j]] === undefined) map[s1[j]] = 0
 if (map[s2[j]] === undefined) map[s2[j]] = 0
 map[s1[j]]++
 map[s2[j]]--
 }

 for (const key in map) {
 if (map[key] !== 0) {
 dp[s1 + s2] = false
 return false
 }
 }

 for (let i = 1; i < s1.length; i++) {
 if (
 (helper(dp, s1.substr(0, i), s2.substr(0, i)) &&
 helper(dp, s1.substr(i), s2.substr(i))) ||
 (helper(dp, s1.substr(0, i), s2.substr(s2.length - i)) &&
 helper(dp, s1.substr(i), s2.substr(0, s2.length - i)))
 ) {
 dp[s1 + s2] = true
 return true
 }
 }

 dp[s1 + s2] = false
 return false
}

export { isScramble }