README.md

Valid Palindrome

Solution 1

Two Pointers

/**
 * Question   : 125. Valid Palindrome
 * Complexity : Time: O(n) ; Space: O(1)
 * Topics     : String
 */
class Solution {
    public boolean isPalindrome(String s) {
        if (s == null || s.length() == 0) {
            return true;
        }

        int low = 0;
        int high = s.length() - 1;

        while (low < high) {
            while (low < high && !Character.isLetterOrDigit(s.charAt(low))) {
                low++;
            }
            while (low < high && !Character.isLetterOrDigit(s.charAt(high))) {
                high--;
            }
            if (low < high && Character.toLowerCase(s.charAt(low)) != Character.toLowerCase(s.charAt(high))) {
                return false;
            }
            low++;
            high--;
        }

        return true;
    }
}