cppreference.com > C++ Algorithms > set_intersection set_intersection Syntax:
      #include <algorithm>
      iterator set_intersection( iterator start1, iterator end1, iterator start2, iterator end2, iterator result );
      iterator set_intersection( iterator start1, iterator end1, iterator start2, iterator end2, iterator result, StrictWeakOrdering cmp );
The set_intersection() algorithm computes the intersection of the two sets defined by [start1,end1) and [start2,end2) and stores the intersection starting at result. Both of the sets, given as ranges, must be sorted in ascending order. The return value of set_intersection() is an iterator to the end of the intersection range. If the strict weak ordering comparison function object cmp is not specified, set_intersection() will use the < operator to compare elements. Related topics: includes set_difference set_symmetric_difference set_union