set_union.cpp

 /*
    Author : Thamara Andrade
    Date : Date format 02/09/2019
    Time : Time format 02:00
    Description : Computes the union of two ranges.
*/

#include <iostream>
#include <vector>
#include <algorithm>

int main(){
    std::vector<int> v1 {3, 1, 5};
    std::vector<int> v2 {1, 0};

    // the destination needs to fit all merged values, we'll prune the extra elements later
    std::vector<int> destination(v1.size() + v2.size());

    // set_union requires sorted ranges
    std::sort(v1.begin(), v1.end());
    std::sort(v2.begin(), v2.end());

    // returns iterator to the end of the constructed range
    auto it = std::set_union(v1.begin(), v1.end(),  // first range 
                             v2.begin(), v2.end(),  // second range
                             destination.begin());

    // prune extra values
    destination.resize(it - destination.begin()); 

    // destination is now {0, 1, 3, 5}
    for (auto value : destination) { 
        std::cout << value << " "; 
    }
    return 0;
}