leetcode Valid Palindrome 难度系数2 2.25

Question:

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.

public class Solution {
public boolean isPalindrome(String s) {
if (s == null || s.length() == 0) {
return true;
}
String sUsed = s.toLowerCase().trim();
int left = 0;
int right = sUsed.length() - 1;
while (left < right) {
if (!(sUsed.charAt(left) <= 'z' && sUsed.charAt(left) >= 'a')
&& !(sUsed.charAt(left) <= '9' && sUsed.charAt(left) >= '0')) {
++left;
} else if (!(sUsed.charAt(right) <= 'z' && sUsed.charAt(right) >= 'a')
&& !(sUsed.charAt(right) <= '9' && sUsed.charAt(right) >= '0')) {
--right;
} else if (sUsed.charAt(right) != sUsed.charAt(left)) {
return false;
} else if (sUsed.charAt(right) == sUsed.charAt(left)) {
++left;
--right;
}

}
return true;
}
}