c++ primer 5th 练习11.17关于map,set和copy算法

#include <string>
#include <iostream>
#include <list>
#include <vector>
#include <set>
#include <map>

using namespace std;

void print_set(const multiset<string> &);
void print_vec(const vector<string> &);
int main()
{
//first one:
multiset<string> c{"m1","m2","m3","m4","m5"};
vector<string> v{"str1","str2","str3","str4","str5"};
copy(v.begin(),v.end(),inserter(c,c.end()));
print_set(c);
print_vec(v);

//second one:this one is reported wrong.
//copy(v.begin(),v.end(),back_inserter(c));

//third:
copy(c.begin(),c.cend(),inserter(v,v.begin()));
print_set(c);
print_vec(v);

//fourth:
copy(c.begin(),c.cend(),back_inserter(v));
print_set(c);
print_vec(v);

  return 0;

}

void print_set(const multiset<string>