java 87. Scramble String（＃）。java

Posted 2021-05-08

public class Solution {
    public boolean isScramble(String s1, String s2) {
        if(s1.length() != s2.length())
            return false;
        return isScramble_rec(s1, s2, 0, s1.length() - 1, 0, s2.length() - 1);
    }
    private boolean isScramble_rec(String str1, String str2, int s1, int e1, int s2, int e2){
        if(s1 > e1)
            return true;
        if(s1 == e1)
            return str1.charAt(s1) == str2.charAt(s2);
        int[] tail = new int[26];
        int[] head = new int[26];
        int h = s2, e = e2;
        int diffh = 0, diffe = 0;
        int i;
        for(i = s1; i <= e1 - 1; i++){
            if(++head[str1.charAt(i) - 'a'] <= 0)
                diffh--;
            else
                diffh++;
            if(++tail[str1.charAt(i) - 'a'] <= 0)
                diffe--;
            else
                diffe++;
            if(--head[str2.charAt(h++) - 'a'] >= 0)
                diffh--;
            else
                diffh++;
            if(--tail[str2.charAt(e--) - 'a'] >= 0)
                diffe--;
            else
                diffe++;
            if(diffh == 0){
                if(isScramble_rec(str1, str2, s1, i, s2, h-1) && isScramble_rec(str1, str2, i + 1, e1, h, e2))
                    return true;
            }
            if(diffe == 0){
                if(isScramble_rec(str1, str2, s1, i, e + 1, e2) && isScramble_rec(str1, str2, i + 1, e1, s2, e))
                    return true;
            }
        }
        return false;
    }
}

public class Solution {
    public boolean isScramble(String s1, String s2) {
        if (s1.equals(s2)) return true; 
        
        int[] letters = new int[26];
        for (int i=0; i<s1.length(); i++) {
            letters[s1.charAt(i)-'a']++;
            letters[s2.charAt(i)-'a']--;
        }
        for (int i=0; i<26; i++) if (letters[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(s2.length()-i)) 
             && isScramble(s1.substring(i), s2.substring(0,s2.length()-i))) return true;
        }
        return false;
    }
}