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.

 

应该算是leetcode上最简单的题之一了吧。双指针可搞定。。

1     public boolean isPalindrome(String s) { 2         int i=0; 3         int j=s.length()-1; 4         while(i