Determine elements that are in either or both sets : set_union « STL Algorithms Merge « C++ Tutorial

1. C++ Tutorial
2. STL Algorithms Merge
3. set_union

#include <iostream>
using std::cout;
using std::endl;

#include <algorithm>
#include <iterator>

int main()
{
   const int SIZE1 = 10, SIZE2 = 5, SIZE3 = 20;
   int a1[ SIZE1 ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
   int a2[ SIZE2 ] = { 4, 5, 6, 7, 8 };
   int a3[ SIZE2 ] = { 4, 5, 6, 11, 15 };
   std::ostream_iterator< int > output( cout, " " );

   std::copy( a1, a1 + SIZE1, output );
   cout << "\n";
   std::copy( a2, a2 + SIZE2, output );
   cout << "\n";
   std::copy( a3, a3 + SIZE2, output );

   int unionSet[ SIZE3 ];

   int *ptr = std::set_union( a1, a1 + SIZE1, a3, a3 + SIZE2, unionSet );
   cout << "set_union of a1 and a3 is: ";
   std::copy( unionSet, ptr, output );
   cout << endl;

   return 0;
}

1 2 3 4 5 6 7 8 9 10
4 5 6 7 8
4 5 6 11 15 set_union of a1 and a3 is: 1 2 3 4 5 6 7 8 9 10 11 15