inline bool lt_nocase(char c1, char c2) { return tolower(c1) < tolower(c2); }

int main() {

 int A1[] = {1, 3, 5, 7, 9, 11};

 int A2[] = {1, 1, 2, 3, 5, 8, 13};

 char A3[] = {'a', 'b', 'b', 'B', 'B', 'f', 'h', 'H'};

 char A4[] = {'A', 'B', 'B', 'C', 'D', 'F', 'F', 'H' };

 const int N1 = sizeof(A1) / sizeof(int);

 const int N2 = sizeof(A2) / sizeof(int);

 const int N3 = sizeof(A3);

 const int N4 = sizeof(A4);

 cout << "Intersection of A1 and A2: ";

 set_intersection(A1, A1 + N1, A2, A2 + N2, ostream_iterator(cout, " "));

 cout << endl << "Intersection of A3 and A4: ";

 set_intersection(A3, A3 + N3, A4, A4 + N4, ostream_iterator(cout, " "), lt_nocase);

 cout << endl;

}

The output is

Intersection of A1 and A2: 1 3 5

Intersection of A3 and A4: a b b f h