C++ STL merge,set_union,set_intersection,set_difference,set_symmetric_difference

default (1)	template <class InputIterator1, class InputIterator2, class OutputIterator> OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);
custom (2)	template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare> OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);

set_difference：只存在第一区间，不存在于第二区间的元素，如果原区间存在重复的元素，目标区间重复元素的个数是拿第一个区间的元素的个数减去第二区间的元素的个数，如果为负数，则目标区间对应重复元素的个数为0.

default (1)	template <class InputIterator1, class InputIterator2, class OutputIterator> OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);
custom (2)	template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare> OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);

set_intersection：目标区间的元素不但存在于第一区间，同时也存在于第二区间，如果源区间存在重复元素，目标区间也会有重复元素，目标区间重复元素的个数是源区间内的重复个数较小的值。

default (1)	template <class InputIterator1, class InputIterator2, class OutputIterator> OutputIterator set_symmetric_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);
custom (2)	template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare> OutputIterator set_symmetric_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);

set_symmetric_difference：目标元素区间内的元素存在于第一区间或存在于第二区间，但不同时存在于两个源区间；

如果源区间存在重复元素，目标区间也会有重复元素，目标区间重复元素的个数是两源区间内的重复个数差额。

#include "algostuff.hpp"

#include <iterator>

#include <ostream>

using namespace std;

int main(){
int array_1[] = {1,2,2,4,6,7,7,9};
int array_1_count = sizeof(array_1)/sizeof(int);

int array_2[] = {2,2,2,3,6,6,8,9};
int array_2_count = sizeof(array_2)/sizeof(int);

cout<<"array_1:";
copy(array_1,array_1+array_1_count,ostream_iterator<int>(cout," "));
cout<<endl;
cout<<"array_2:";
copy(array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;

cout<<"merge():";
merge(array_1,array_1+array_1_count,array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;

cout<<"set_union:";

set_union(array_1,array_1+array_1_count,array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;

cout<<"set_intersection():";
set_intersection(array_1,array_1+array_1_count,array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;

cout<<"set_difference():";
set_difference(array_1,array_1+array_1_count,array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;
cout<<"set_symmetric_difference():";
set_symmetric_difference(array_1,array_1+array_1_count,array_2,array_2+array_2_count,ostream_iterator<int>(cout," "));
cout<<endl;

return 0;

}

编译后输出：

array_1:1 2 2 4 6 7 7 9 

array_2:2 2 2 3 6 6 8 9 

merge():1 2 2 2 2 2 3 4 6 6 6 7 7 8 9 9 

set_union:1 2 2 2 3 4 6 6 7 7 8 9 

set_intersection():2 2 6 9 

set_difference():1 4 7 7 

set_symmetric_difference():1 2 3 4 6 7 7 8