参考自:http://www.cplusplus.com/reference/algorithm/set_intersection/
set_intersection
//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);
从result指向的位置开始,有序地加入两个有序集合[first1,last1)范围和[first2,last2)范围的交集。第一个版本使用操作符<比较元素,第二个版本使用comp函数比较元素。两个集合中的元素应该按照相同的规则进行了排序(操作符<或comp函数),结果也将有序。
- 实现
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result)
{
while (first1!=last1 && first2!=last2)
{
if (*first1<*first2) ++first1;
else if (*first2<*first1) ++first2;
else {
*result = *first1;
++result; ++first1; ++first2;
}
}
return result;
}
- 示例
#include <iostream> // std::cout
#include <algorithm> // std::set_intersection, std::sort
#include <vector> // std::vector
int main () {
int first[] = {5,10,15,20,25};
int second[] = {50,40,30,20,10};
std::vector<int> v(10); // 0 0 0 0 0 0 0 0 0 0
std::vector<int>::iterator it;
std::sort (first,first+5); // 5 10 15 20 25
std::sort (second,second+5); // 10 20 30 40 50
it=std::set_intersection (first, first+5, second, second+5, v.begin());
// 10 20 0 0 0 0 0 0 0 0
v.resize(it-v.begin()); // 10 20
std::cout << "The intersection has " << (v.size()) << " elements:\n";
for (it=v.begin(); it!=v.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}/*Output
The intersection has 2 elements:
10 20
*/