C++/STL Algorithms Merge/set difference

Determine elements in one set but not in another set

<source lang="cpp">

1. include <iostream>

using std::cout; using std::endl;

1. include <algorithm>
2. 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, 7, 6, 11, 15 };
  std::ostream_iterator< int > output( cout, " " );
  cout << "a1 contains: ";
  std::copy( a1, a1 + SIZE1, output );
  cout << "\na2 contains: ";
  std::copy( a2, a2 + SIZE2, output );
  cout << "\na3 contains: ";
  std::copy( a3, a3 + SIZE2, output );
  int difference[ SIZE1 ];
  int *ptr = std::set_difference( a1, a1 + SIZE1, a2, a2 + SIZE2, difference );
  cout << "\n\nset_difference of a1 and a2 is: ";
  std::copy( difference, ptr, output );
  return 0;

} /* a1 contains: 1 2 3 4 5 6 7 8 9 10 a2 contains: 4 5 6 7 8 a3 contains: 4 7 6 11 15 set_difference of a1 and a2 is: 1 2 3 9 10

*/        
 </source>

Determine elements of first range without elements of second range by using set_difference()

<source lang="cpp">

/* 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.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. 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;
   // determine elements of first range without elements of second range by using set_difference()
   cout << "set_difference():           ";
   set_difference (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_difference(): 1 4 7 7

*/       
 </source>