题目：
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.
Example Questions Candidate Might Ask:
Q: What about an empty string? Is it a valid palindrome?
A: For the purpose of this problem, we define empty string as valid palindrome.
解答：
使用两个游标
public boolean isPalindrome(String s) { int i = 0; int j = s.length()-1; while(i < j) { while(i < j && !Character.isLetterOrDigit(s.charAt(i))) { i++; } while(i < j && !Character.isLetterOrDigit(s.charAt(j))) { j--; } if(Character.toLowerCase(s.charAt(j) != Character.toLowerCase(s.charAt(i))) { return false; } i++; j--; } return true; }
原文：https://www.cnblogs.com/wylwyl/p/10346245.html