125. Valid Palindrome - jiejackyzhang/leetcode-note GitHub Wiki
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.
String类题目。
解题思路为two pointers。 左右指针从首尾开始分别确定一个字符，然后比较。
public class Solution {
public boolean isPalindrome(String s) {
if(s == null || s.length() == 0) return true;
int left = 0;
int right = s.length() - 1;
s = s.toLowerCase();
while(left < right) {
while(left < right && !Character.isLetterOrDigit(s.charAt(left))) left++;
while(left < right && !Character.isLetterOrDigit(s.charAt(right))) right--;
if(s.charAt(left) != s.charAt(right)) return false;
left++;
right--;
}
return true;
}
}