rewrite

Author: mengli

ScrambleString.java

@@ -1,7 +1,3 @@
-
-
-import java.util.Arrays;
-
 /** 
  * Given a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively.
  *
@@ -43,39 +39,33 @@
 
 public class ScrambleString {
 	public boolean isScramble(String s1, String s2) {
-		int length1 = s1.length();
-		int length2 = s2.length();
-		if (length1 != length2)
+		if (s1.length() != s2.length())
 			return false;
-
-		if (length1 == 0 || s1.equals(s2))
+		if (s1.equals(s2))
 			return true;
 
-		char[] ca1 = s1.toCharArray();
-		char[] ca2 = s2.toCharArray();
-		Arrays.sort(ca1);
-		Arrays.sort(ca2);
-		if (!Arrays.equals(ca1, ca2))
-			return false;
+		int[] A = new int[26];
+		for (int i = 0; i < s1.length(); i++) {
+			++A[s1.charAt(i) - 'a'];
+		}
 
-		int i = 1;
-		while (i < length1) {
-			String a1 = s1.substring(0, i);
-			String b1 = s1.substring(i, length1);
-			String a2 = s2.substring(0, i);
-			String b2 = s2.substring(i, length2);
-			if (a1.equals(b2) && b1.equals(a2))
-				return true;
-			boolean r = isScramble(a1, a2) && isScramble(b1, b2);
-			if (!r) {
-				String c2 = s2.substring(0, length1 - i);
-				String d2 = s2.substring(length1 - i);
-				r = isScramble(a1, d2) && isScramble(b1, c2);
-			}
-			if (r)
-				return true;
-			i++;
+		for (int j = 0; j < s2.length(); j++) {
+			--A[s2.charAt(j) - 'a'];
+		}
+
+		for (int k = 0; k < 26; k++) {
+			if (A[k] != 0) return false;
+		}
+
+		for (int i = 1; i < s1.length(); i++) {
+			boolean result = isScramble(s1.substring(0, i), s2.substring(0, i)) && isScramble(s1.substring(i), s2.substring(i));
+			result = result || (isScramble(s1.substring(0, i), s2.substring(s2.length() - i, s2.length())) && isScramble(s1.substring(i), s2.substring(0, s2.length() - i)));
+			if (result) return true;
 		}
 		return false;
 	}
+	
+	public static void main(String[] args) {
+		System.out.println(new ScrambleString().isScramble("aab", "bab"));
+	}
 }