public static int palindromeIndex(String s) {
        //goal: find idx of char that will make str a palindrome when its removed
        if(s.length() == 1) return -1; //already a palindrome
        
        //use two pointers to iterate from left and right of str
        int left = 0, right = s.length() - 1;
        while(left < right){
           char leftChar = s.charAt(left);
           char rightChar = s.charAt(right);
           //if left pointer != right pointer, check which idx will make a palindrome if removed
           if(leftChar != rightChar){
                if(isPalindrome(s, left + 1, right)) return left;
                else return right;
           }
            left++;
            right--;
        }
        return -1; //str is already a palindrome
    }
    
    //uses two pointers to make sure chars are mirrored
    public static boolean isPalindrome(String s, int left, int right){
        while(left < right){
            if(s.charAt(left) != s.charAt(right)) return false; //chars arent mirrored
            left++;
            right--;
        }
        return true;
    }