back_insert_iterator和insert_iterator

#include <iostream>
#include <string>
#include <iterator>
#include <vector>
#include <algorithm>

void output(const std::string & s){std::cout << s << " ";}

int main()
{
    using namespace std;
    string s1[4]={"fine", "fish", "fashion", "fate"};
    string s2[2]={"busy", "bats"};
    string s3[2]={"silly", "singers"};
    vector<string> words(4);
    copy(s1,s1+4,words.begin());
    for_each(words.begin(),words.end(),output);
    cout << endl;
    copy(s2,s2+2,back_insert_iterator<vector<string> >(words));
    for_each(words.begin(),words.end(),output);
    cout << endl;

    copy(s3,s3+2,insert_iterator<vector<string> >(words,words.begin()));
    for_each(words.begin(),words.end(),output);
    cout << endl;
    return 0;
}