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

valid-palindrome.java

class Solution {
    public boolean isPalindrome(String s) {
        int l = 0;
        int r = s.length() - 1;
        while(l < r) {
            
            while(l < r && !Character.isLetter(s.charAt(l)) && !Character.isDigit(s.charAt(l)) ) {
                l++;
            }
            char lc = Character.toLowerCase(s.charAt(l));
            while(r > l && !Character.isLetter(s.charAt(r)) && !Character.isDigit(s.charAt(r)) ) {
                r--;
            }
            char rc = Character.toLowerCase(s.charAt(r));
            if (lc != rc) {
                return false;
            }
            l++;
            r--;
        }
        return true;
    }
}