std::set_symmetric_difference is an STL algorithm to obtain the elements from two containers which are in only one of these containers.


#include <algorithm>

#include <cassert>

#include <vector>



int main()

{

  std::vector<int> evens;

  evens.push_back(2);

  evens.push_back(4);



  std::vector<int> primes;

  primes.push_back(2);

  primes.push_back(3);



  std::vector<int> result;



  std::set_symmetric_difference(

    evens.begin(),evens.end(),

    primes.begin(), primes.end(),

    std::back_inserter(result));



  //Assume that the result consists of

  //- a '3' (a non-even prime) 

  //- a '4' (a non-prime even)

  assert(result.size() == 2);

  assert(result[0] == 3 || result[0] == 4);

  assert(result[1] == 3 || result[1] == 4);

  assert(result[0] != result[1]);

}

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(C++) std::set_symmetric_difference