I have a (very simple) C++ code, and this is my method (a standard method from cppreference.com ) :

V vector intersection(std: : vector v1, std: : vector v2) { 10 std: : vector v3; 11 12 std: : sort(v1 . begin(), v1.end() ) ; 13 std: : sort(v2. begin(), v2.end() ); 14 15 std: : set_intersection(v1 . begin() , v1. end(), 16 v2.begin( ) , v2. end( ), 17 back_inserter (v3) ) ; 18 return v3; 1921 int main() { 22 map > set; 23 vector v1, v2, v3; 24 set [1] . push_back(1); set[1]. push_back(2); 25 set [2] . push_back(3); set[2]. push_back(4); 26 set [3] . push_back(2); set[3].push_back(5); 27 cout