LeetCode 125: Valid Palindrome

问题描述

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: “A man, a plan, a canal: Panama”
Output: true
Example 2:

Input: “race a car”
Output: false

实现

class Solution {
    public boolean isPalindrome(String s) {
        String ss = s.replaceAll("[^0-9a-zA-Z]", "").toLowerCase();
        if (s.length() == 0 || ss.length()<=1 )
            return true;
        int ps = 0;
        int pe = ss.length() - 1;
        boolean result = true;
        while (ps <= pe) {
            if (ss.charAt(ps++) != ss.charAt(pe--)) {
                result = false;
                break;
            }
        }
        return result;
    }
}