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.
思路：双指针夹逼，判断首位对应的字母是否相同。Character.isLetterOrDigit这个method好好用！Reverse Words in String就可以用这个method和stack读出来words，然后pop出来。
public class Solution { public boolean isPalindrome(String s) { int i=0,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(i))!=Character.toLowerCase(s.charAt(j))) { return false; } i++; j--; } return true; } }
原文：http://www.cnblogs.com/Machelsky/p/5944455.html