如何使用集合中的元素键擦除地图中的元素？

std::set<std::string> keys;
std::map<std::string, std::string> mymap;
....
for_each(keys.begin(), keys.end(), boost::bind(&std::map<std::string,   
                                               std::string>::erase, 
                                               &mymap, _1));

for (std::set<std::string>::iterator it(keys.begin()); it != keys.end(); ++it)
{
    mymap.erase(*it);
}

std::for_each(keys.begin(), keys.end(), [&mymap](const std::string& key)
{
    mymap.erase(key);
});

bind

erase

struct assoc_erase
{
    typedef void result_type;

    template <typename TContainer, typename TKey>
    void operator()(TContainer* container, const TKey& key)
    {
        container->erase(key);
    }
};

// Used as:
std::for_each(keys.begin(), keys.end(), std::bind(assoc_erase(), &mymap, _1));