how to find the intersection of two std::set in C++?

Question

I have been trying to find the intersection between two std::set in C++, but I keep getting an error.

I created a small sample test for this

#include         


        

Answer 1

You havent provided an output iterator for set_intersection

template 
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
                                InputIterator2 first2, InputIterator2 last2,
                                OutputIterator result );

Fix this by doing something like

...;
set intersect;
set_intersection(s1.begin(),s1.end(),s2.begin(),s2.end(),
                  std::inserter(intersect,intersect.begin()));

You need a std::insert iterator since the set is as of now empty. We cannot use back_ or front_inserter since set doesnt support those operations.