如何在c++ 11的迭代器中获得关于auto标识符的更多细节

 void test()
 {
       vector <string> s={"hello world"};
       for(vector<string>::iterator it=s.begin();it!=s.end()&&!it->empty();it++)
      {
           for(auto it2=it->begin();it2!=it->end();it2++)//I don't konw  type of it2
           {
                *it2=toupper(*it2);
           }
       cout<<*it<<endl;
     }
}
 void test()
 {
       vector <string> s={"hell