bool search(int n, int i, int j, string s1, string s2) {
    if (dp[n][i][j] != -1) {
        return dp[n][i][j];
    }

    if (n == 1) {
        return dp[1][i][j] = s1[i] == s2[j];
    }

    for (int len = 1; len < n; len++) {
        bool flag1 = search(len, i, j, s1, s2) && search(n - len, i + len, j + len, s1, s2);
        bool flag2 = search(len, i, j + n - len, s1, s2) && search(n - len, i + len, j, s1, s2);
        if (flag1 || flag2) {
            return dp[n][i][j] = true;
        }
    }

    return dp[n][i][j] = false;
}

vector<vector<vector<int>>> dp;
bool isScramble(string s1, string s2) {
    int n = s1.length();
    if (n != s2.length()) { 
        return false;
    }

    dp = vector<vector<vector<int>>>(n + 1,
                                     vector<vector<int>>(n, vector<int>(n, -1)));
    return search(n, 0, 0, s1, s2);
}