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