Leetcode (Java) -125. Palindromic sequence verification

Given a string, verify that it is a palindrome string, consider only the alphabetic and numeric characters, can ignore letter case.

Description: In this problem, we define the empty string as a valid palindromic sequence.

Example 1:

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

Input: "race a car"
Output: false

Thinking: This is a study of the palindrome title, and is the simplest form, that is, whether a string is a palindrome.

To address this problem, we can use the dual head and tail pointer,

• If two pointers are different elements, the process directly returns false,
• If the two pointers same elements, we also update the head and tail pointers the loops. Until the head and tail pointers meet.

class Solution {
    public boolean isPalindrome(String s) {
        int i=0;int j=s.length()-1;
        while(i<j)
        {
            if(!Character.isLetterOrDigit(s.charAt(i))){
                i++;
                continue;
            }
            if(!Character.isLetterOrDigit(s.charAt(j))){
                j--;
                continue;
            }
            if(Character.toLowerCase(s.charAt(i))!=Character.toLowerCase(s.charAt(j)))
                return false;

            i++;j--;
        }
        return true;
    }
}