set器皿有没有插入迭代器

set容器有没有插入迭代器
我想弄个交并差的集合，应用了set容器和set_union等算法，可是这个方法需要一个输出迭代器，我不知道这个迭代器应该怎么写

#include "stdafx.h"

using namespace std;

int main()

{

   set<int>a,b;

   set<int>uni,intersection,dif;

   int n,m,num;

   cin>>n;

   for(int i=0;i<n;++i)

   {

       cin>>num;

       a.insert(num);

   }

   for(int i=0;i<m;++i)

   {

       cin>>num;

       b.insert(num);

   }

//底下三个都报错了……

   set_union(a.begin(),a.end(),b.begin(),b.end(),back_inserter(uni));

   set_intersection(a.begin(),a.end(),b.begin(),b.end(),back_inserter(intersection));

   set_difference(a.begin(),a.end(),b.begin(),b.end(),back_inserter(dif));

   copy(uni.begin(),uni.end(),ostream_iterator<int>(cout,"\n"));

}

------解决方案--------------------

   set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(uni,uni.end()));

   set_intersection(a.begin(),a.end(),b.begin(),b.end(),inserter(intersection,intersection.end()));

   set_difference(a.begin(),a.end(),b.begin(),b.end(),inserter(dif,dif.end()));

------解决方案--------------------
仅供参考

#include <algorithm>

#include <iostream>

#include <functional>

#include <cstring>

using namespace std;

int main() {

    char *Alphabet = "abcdefghijklmnopqrstuvwxyz" ;

    char *Vowels   = "aeiou" ;

    char *AlphaNum = "0123456789abcdef" ;

    char result[45] ;

    char *last ;


    int lenA  = strlen(Alphabet) ;

    int lenV  = strlen(Vowels  ) ;

    int lenAN = strlen(AlphaNum) ;


    cout << "Alphabet = " << Alphabet << endl ;

    cout << "Vowels   = " << Vowels   << endl ;

    cout << "AlphaNum = " << AlphaNum << endl ;


    cout << "\nusing non-predicate versions" << endl ;


    //non-predicate set_difference

    last = set_difference(Alphabet, Alphabet+lenA,

                          AlphaNum, AlphaNum+lenAN,

                          result) ;

    *last = 0 ;

    cout << "set_difference(Alphabet, AlphaNum) =  " << result << endl ;


    //non-predicate set_intersection

    last = set_intersection(Alphabet, Alphabet+lenA,

                            AlphaNum, AlphaNum+lenAN,

                            result) ;

    *last = 0 ;

    cout << "set_intersection(Alphabet, AlphaNum) =  " << result << endl ;


    //non-predicate set_symmetric_difference

    last = set_symmetric_difference(Alphabet, Alphabet+lenA,

                                    Vowels  , Vowels  +lenV,

                                    result) ;

    *last = 0 ;

    cout << "set_symmetric_difference(Alphabet, Vowels) =  " << result << endl ;


    //non-predicate set_union

    last = set_union(Alphabet, Alphabet+lenA,

                     AlphaNum, AlphaNum+lenAN,

                     result) ;