#include <iostream>
#include <algorithm>
#include <iterator>
#include <vector>
#include <string>
using std::cout;
using std::endl;
using std::string;
using std::vector;
int main()
{
string s1("abcdefg");
string s2("befghijk");
vector<char> vec1(s1.begin(), s1.end());
vector<char> vec2(s2.begin(), s2.end());
vector<char> vec1vec2;
set_union(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), back_inserter(vec1vec2));
copy(vec1vec2.cbegin(), vec1vec2.cend(), std::ostream_iterator<char>(cout, " "));
cout << endl;
return 0;
}
/*
run:
a b c d e f g h i j k
*/