在C++中创建常量集合的标准方法是将值作为两个集合的并/交？

#include <iostream>
#include <set>

int main() {
    std::set<int> constantSet;
    
    constantSet.insert(1);
    constantSet.insert(2);
    constantSet.insert(3);
    
    // 输出集合中的元素
    for (const auto& value : constantSet) {
        std::cout << value << " ";
    }
    
    return 0;
}

#include <iostream>
#include <set>
#include <algorithm>
#include <iterator>

int main() {
    std::set<int> set1 = {1, 2, 3};
    std::set<int> set2 = {2, 3, 4};
    
    std::set<int> unionSet;
    std::set<int> intersectionSet;
    
    std::set_union(set1.begin(), set1.end(), set2.begin(), set2.end(), std::inserter(unionSet, unionSet.begin()));
    std::set_intersection(set1.begin(), set1.end(), set2.begin(), set2.end(), std::inserter(intersectionSet, intersectionSet.begin()));
    
    // 输出并集和交集
    std::cout << "Union: ";
    for (const auto& value : unionSet) {
        std::cout << value << " ";
    }
    
    std::cout << std::endl;
    
    std::cout << "Intersection: ";
    for (const auto& value : intersectionSet) {
        std::cout << value << " ";
    }
    
    return 0;
}