public boolean isScramble(String s1, String s2) {

if(s1.equals(s2)) return true;

if(s1.length()!=s2.length()) return false;

int[] cur_map = new int[26];

for(int i=0; i<s1.length(); i++){

cur_map[s1.charAt(i)-'a']++;

cur_map[s2.charAt(i)-'a']--;

}

for(int i=0; i<26; i++) if(cur_map[i]!=0) return false;

for(int i=1; i<s1.length(); i++){

if( isScramble(s1.substring(0,i), s2.substring(0,i)) && isScramble(s1.substring(i), s2.substring(i))) return true;

if( isScramble(s1.substring(0,i), s2.substring(s1.length()-i)) && isScramble(s1.substring(i), s2.substring(0,s1.length()-i))) return true;

}

return false;

}