Valid Palindrome

class Solution {
public:

    bool isPalindrome(string s) {

        string old = s;
  
        reverse(old.begin(),old.end());

       
        string tmp1,tmp2;
         for(int i = 0; i < s.length();i++)
        {
            tmp1+=((char)(tolower(old[i])));
             tmp2+=((char)(tolower(s[i])));
        }
    
       
                 auto it = std::remove_if(tmp1.begin(), tmp1.end(), [](char const &c) {
        return !std::isalnum(c);
    });
    
    tmp1.erase(it, tmp1.end());
                        auto it2 = std::remove_if(tmp2.begin(), tmp2.end(), [](char const &c) {
        return !std::isalnum(c);
    });
    
    tmp2.erase(it2, tmp2.end());
       
        if(tmp1==tmp2)
        {
            return true;
        }
        else
        {
            return false;
        }
    }   
};