#include<set>
#include<iostream>
#include<algorithm>
#include<iterator>
using namespace std;template <class T>
struct display
{void operator()(const T& x){cout<<x<<" ";}
};int main()
{int ia1[6] = {1,3,5,7,9,11};int ia2[7] = {1,2,3,5,8,13,1};multiset<int> s1(ia1, ia1+6);multiset<int> s2(ia2, ia2+7);for_each(s1.begin(), s1.end(), display<int>());cout<<endl;for_each(s2.begin(), s2.end(), display<int>());cout<<endl;cout<<"union"<<endl;set_union(s1.begin(), s1.end(), s2.begin(), s2.end(), ostream_iterator<int>(cout, " "));cout<<endl;cout<<"intersection"<<endl;set_intersection(s1.begin(), s1.end(), s2.begin(), s2.end(), ostream_iterator<int>(cout, " "));cout<<endl;cout<<"difference"<<endl;set_difference(s1.begin(), s1.end(), s2.begin(), s2.end(), ostream_iterator<int>(cout, " "));cout<<endl;cout<<"difference"<<endl;set_difference(s2.begin(), s2.end(), s1.begin(), s1.end(), ostream_iterator<int>(cout, " "));cout<<endl;cout<<"symmetric difference"<<endl;set_symmetric_difference(s1.begin(), s1.end(), s2.begin(), s2.end(), ostream_iterator<int>(cout, " "));cout<<endl;system("pause");
}

set_union(first1, last1, first2, last2, result)
{while(first1!=last1 && first2!=last2){//两个容器内的元素相比较，把较小者放入结果容器中，并向前移动迭代器//如果两个元素相等则写入结果中，同时移动两个迭代器if(*first1<*first2){*result = *first;++first1;}else if(*first2<*first1){*result = *first;++first2;}else{*result = *first1;++first1;++first2;}++result;}//把剩余的元素都拷贝进结果中//copy返回迭代器指向目标容器的插入元素的最后一个元素的下一个元素return copy(first2, last2, copy(first1, last1, result));
}

set_intersection(first1, last1, first2, last2, result)
{while(first1!=last1 && first2!=last2){if(*first1<*first2){++first1;}else if(*first2<*first1){++first2;}else{*result = *first1;++first1;++first2;++result;}}return result;
}

set_difference(first1, last1, first2, last2, result)
{while(first1!=last1 && first2!=last2){if(*first1<*first2){*result = *first1;++first;++result;}else if(*first2<*first1){++*first2;}else{++first1;++first2;}}return copy(first1, last1, result);
}

set_symmetric_difference(first1, last1, first2, last2, result)
{while(first1!=last1 && first2!=last2){if(*first1<*first2){*result = *first1;++first1;++result;}if(*first2<*first1){*result = *first2;++first2;++result;}else{++first1;++first2;}}return copy(first1, last1, copy(first2, last2, result));
}