text: class Solution {
  public:
      bool isPalindrome(string s) {
          auto left = s.begin();
          auto right = s.end() - 1;
          
          while (left < right) {
              while (!isalnum(*left) && left < right) {
                  left++;
              }
              while (!isalnum(*right) && left < right) {
                  right--;
              }
              if (left >= right) {
                  break;
              }
              if (tolower(*left) != tolower(*right)) {
                  return false;
              }
              left++;
              right--;
          }
          
          return true;
      }
  };
  