public boolean isPalindrome(String s) {
		if(s==null) return false;
		if(s.isEmpty()) return true;
		
		int low=0,high=s.length()-1;
		for(;;){
			while(low<=high && !isAlphaNumeric(s.charAt(low))){
				low++;
			}
			
			while(low<=high && !isAlphaNumeric(s.charAt(high))){
				high--;
			}
			
			if(low>high){
				break;
			}else{
				if(transfer(s.charAt(low))==transfer(s.charAt(high))){
					low++;high--;
				}else{
					return false;
				}
			}
		}
		return true;
    }