使用复印功能打印集

我遇到的问题是，我需要使用copy函数打印union_set函数的结果集。（所以我不允许把输出作为set_union函数的最后一项）。对于最后一个AunionB指针，我似乎无法使copy函数正常工作（我还必须再做几次）。我目前所做的只是我最后一次尝试答案，尽管我尝试了更多的事情。我在复制功能上做错了什么？这是代码。

#include <iostream>
#include <iterator>
#include <set>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
    int setA[5] = {2, 4, 5, 7, 8};
    int setB[7] = {1, 2, 3, 4, 5, 6, 7};
    int setC[5] = {2, 5, 8, 8, 15};
    int setD[6] = {1, 4, 4, 6, 7, 12};
    set<int> set2A(setA,setA+5);
    set<int> set2B(setB,setB+7);
    set<int> set2C(setC,setC+5);
    set<int> set2D(setD,setD+6);

    int AunionB[12];
    int AunionC[10];
    int BunionD[13];
    int AintersectB[12];
    int AintersectC[10];
    set<int> finalUnion;
    set<int> finalIntersection;
    set<int> final2Union;
    set<int> final2Intersection;
    set<int> final2Difference;
    ostream_iterator< int > output( cout, " " );
    int *lastAunionB;
    int *lastAunionC;
    int *lastBunionD;
    int *lastAintersectB;
    int *lastAintersectC;
    cout << "setA = ";
    copy(set2A.begin(), set2A.end(), output);
    cout << endl;
    cout << "setB = ";
    copy(set2B.begin(), set2B.end(), output);
    cout << endl;
    cout << "setC = ";
    copy(set2C.begin(), set2C.end(), output);
    cout << endl;
    cout << "setD = ";
    copy(set2D.begin(), set2D.end(), output);
    cout << endl;
    //here is where the problem lies
    cout << "AunionB = ";
    lastAunionB = set_union(setA, setA+5, setB, setB+7, AunionB);
    copy(lastAunionB, lastAunionB, output);
    cout << endl;
    /*
    cout << "AunionC = ";
    set_union(setA, setA+5, setC, setC+5, AunionC);
    cout << endl;
    cout << "BunionD = ";
    set_union(setB, setB+7, setD, setD+6, BunionD);
    cout << endl;
    cout << "AintercectB = ";
    set_intersection(setA, setA+5, setB, setB+7, AintersectB);
    cout << endl;
    cout << "AintercectC = ";
    set_intersection(setA, setA+5, setC, setC+7, AintersectC);
    cout << endl;
    */
    return 0;

}