/**
knakul853
**/

class Solution {
public:
    bool isPalindrome(string s) {

       int n = (int)s.size();
        int i=0, j=n-1;

        while( i < j )
        {
            while( i< j && !isalnum(s[i]))i++;
            while( i < j && !isalnum(s[j]))j--;

            if(tolower(s[i]) !=tolower(s[j])) return false;
            i++;
            j--;

        }


        return true;
    }
};