public boolean isIsomorphic(String s, String t) {
		HashMap<Character, Character> map1 = new HashMap<Character, Character>();
		HashMap<Character, Character> map2 = new HashMap<Character, Character>();
		for (int i = 0; i < s.length(); ++i) {
			char sc = s.charAt(i), tc = t.charAt(i);
			if (map1.containsKey(sc)) {
				if (map1.get(sc) != tc)
					return false;
			} else if (map2.containsKey(tc)) {
				if (map2.get(tc) != sc)
					return false;
			} else {
				map1.put(sc, tc);
				map2.put(tc, sc);
			}
		}
		return true;
	}