//迭代器版本
auto i = my_map.begin();
while(i != my_map.end()){
cout << i->first << ":" << i->second << endl;
i ;
}
//另一种写法
for (auto i = my_map.begin(); i != my_map.end(); i)
cout << i->first << ":" << i->second << endl;
//c 11新特性
for(auto i:my_map)
cout << i.first << ":" << i.second <