LeetCode 154题：Valid Palindrome

原题：

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

Solution：

public boolean isPalindrome(String s) {
         if(s == null || s.equals(""))
            return true;
        s = s.toLowerCase();
        for(int start = 0,end = s.length() - 1; start < end; start++,end--) {
            while(start < end && !((s.charAt(start) <= 'z' && s.charAt(start) >= 'a') || (s.charAt(start) <= '9' && s.charAt(start) >= '0')))
                start++;
            while(end > start && !((s.charAt(end) <= 'z' && s.charAt(end) >= 'a') || (s.charAt(end) <= '9' && s.charAt(end) >= '0')))
                end--;
            if(start >= end )
                return true;
            if(s.charAt(start) != s.charAt(end))
                return false;
        }
        return true;
    }

感觉题目也没说清楚那些要计算那些不要计算在内，只看出来空格标点符号这些不算，数字之类的不知道要不要计算。。。。