public static boolean isUniqueChars2(String s) {
		// TODO Auto-generated method stub
		if (s.length() > 26) return false;
		int bits = 0;
		for (int i=0; i < s.length(); i++) {
			int shift = s.charAt(i) - 'a';
			if ((bits & (1 << shift)) > 0) return false;
			else bits |= 1 << shift;
		}
		return true;
	}