0125.cpp

class Solution {
  public:
    bool isPalindrome(string s) {
        int i = 0, j = s.size() - 1;
        while (i < j) {
            if (!isalnum(s[j]))
                j--;
            else if (!isalnum(s[i]))
                i++;
            else if (tolower(s[i]) != tolower(s[j]))
                return false;
            else
                i++, j--;
        }
        return true;
    }
};