LeetCode 125. Valid Palindrome

分析

难度 易

来源

https://leetcode.com/problems/valid-palindrome/

题目

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

解答

Runtime: 6 ms, faster than 72.53% of Java online submissions for Valid Palindrome.

package LeetCode;

public class L125_ValidPalindrome {
    public boolean isPalindrome(String s) {
        s=s.toLowerCase();
        if(s.length()<=1)
            return true;
        int head=0,tail=s.length()-1;
        while(head<=tail){
            if(!Character.isLetterOrDigit(s.charAt(head)))
            {
                head++;
                continue;
            }
            if(!Character.isLetterOrDigit(s.charAt(tail)))
            {
                tail--;
                continue;
            }
            if(s.charAt(head)==s.charAt(tail))
            {
                head++;
                tail--;
            }else
                return false;
        }
        return true;
    }
    public static void main(String[] args){
        L125_ValidPalindrome l125=new L125_ValidPalindrome();
        String s="A man, a plan, a canal: Panama";
        //String s="race a car";
        System.out.println(l125.isPalindrome(s));
    }
}