C++ Tutorial/STL Algorithms Merge/set union

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Determine elements that are in either or both sets

#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

Illustrate set_union

#include <iostream>
#include <cassert>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
  bool result;
  string s("abcde");
  string s2("aeiou");
  vector<char> vector1(s.begin(), s.end());
  vector<char> vector2(s2.begin(), s2.end());
  vector<char> setUnion;
  set_union(vector1.begin(), vector1.end(),vector2.begin(), vector2.end(),back_inserter(setUnion));
  for(int i=0;i<setUnion.size();i++){
    cout << setUnion[i];
  }
  return 0;
}
abcdeiou

unite the ranges by using set_union()

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;
    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << " ";
    }
    std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
 * - fill values from first to last into the collection
 * - NOTE: NO half-open range
 */
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
    for (int i=first; i<=last; ++i) {
        coll.insert(coll.end(),i);
    }
}
using namespace std;
int main()
{
    int c1[] = { 1, 2, 2, 4, 6, 7, 7, 9 };
    int num1 = sizeof(c1) / sizeof(int);
    int c2[] = { 2, 2, 2, 3, 6, 6, 8, 9 };
    int num2 = sizeof(c2) / sizeof(int);
    // print source ranges
    cout << "c1:                         " ;
    copy (c1, c1+num1, ostream_iterator<int>(cout," "));
    cout << endl;
    cout << "c2:                         " ;
    copy (c2, c2+num2, ostream_iterator<int>(cout," "));
    cout << "\n" << endl;
    // unite the ranges by using set_union()
    cout << "set_union():                ";
    set_union (c1, c1+num1, c2, c2+num2, ostream_iterator<int>(cout," "));
    cout << endl;
}
c1:                         1 2 2 4 6 7 7 9
c2:                         2 2 2 3 6 6 8 9
set_union():                1 2 2 2 3 4 6 6 7 7 8 9