Palindrome (c++)

#include <iostream>
#include <string>
using namespace std;

int main(void){
        string s = "abcdef";
        string::iterator pos;
        reverse(s.begin(), s.end());

        string tmp ="";
        for(int i=0; i< s.length(); i++){
                tmp += s[s.length()-i-1];
        }

        for(pos = s.begin(); pos != s.end(); ++pos)
                cout<<*pos;
        cout<<endl;

        cout<<s<<endl;
        cout<<tmp<<endl;
        return 0;
}