Union of two Sets

[neverStopLearning]

I am having trouble understanding how the union is working out. When the union occurs, my set 1 is traversing to its last element then being added, then set 2's element 1 and element 2 are added, then it goes back to set 1's 2nd and 1st element and adds them respectively. But set 2's 3rd element is never added.

Input is: set1 = {10, 11, 12}
set2 = {20,21,22}

Output when union is done: set3 = 12 21 20 11 10

// Set.h header file
#ifndef SET_H
#define SET_H

#include "LinkedBag.h"
using std::ostream;

template<class ItemType>
class Set {
private:
	LinkedBag<ItemType> Bag;
public:
	Set(){
		
	}
	int getCurrentSize();
	void isEmpty();
	bool add(const ItemType& newEntry);
	bool remove(const ItemType& anEntry);
	bool contains(const ItemType& anEntry);
	vector<ItemType> toVector() const;
		Set<ItemType> &operator+( Set<ItemType>& setb){
			vector<ItemType> vector1 = this->toVector();
			vector<ItemType> vector2 = setb.toVector();
			Set<ItemType> *set3 = new Set<ItemType>();

			for (int i = 0; i < getCurrentSize(); i++){
				for (int j = 0; j < setb.getCurrentSize(); j++){
					//checks for matching elements in sets, or if union set already contains element.
					if (!set3->contains(vector1[i])){
						set3->add(vector1[i]);
					}
					else if (!set3->contains(vector2[j]))
						set3->add(vector2[j]);
				}
			}
			return *set3;
		}

		Set<ItemType> &operator-( Set<ItemType>& setb){
			vector<ItemType> vector1 = this->toVector();
			vector<ItemType> vector2 = setb.toVector();
			Set<ItemType> *set3 = new Set<ItemType>();

			for (int i = 0; i < getCurrentSize(); i++){
				for (int j = 0; j < setb.getCurrentSize(); j++){
					if (vector1[i] == vector2[j] && !set3->contains(vector1[i])){
						set3->add(vector1[i]);
					}

				}
			}
			return *set3;
		}

	friend std::ostream& operator<<(ostream &cout, Set<ItemType>& set3){
		vector<ItemType> vec3 = set3.toVector();
		for (int i = set3.getCurrentSize()-1; i >= 0; --i){
			cout << vec3[i] << " ";
		}
		cout << endl;
		return cout;
	}


};
#include "Set.cpp"
#endif

// Implementation File

#ifndef SET_CPP
#define SET_CPP

#include "Set.h"

template<class ItemType>
int Set<ItemType>::getCurrentSize()
{
	return Bag.getCurrentSize();
}
template<class ItemType>
void Set<ItemType>::isEmpty()
{
	Bag.isEmpty();
}
template<class ItemType>
bool Set<ItemType>::add(const ItemType& newEntry)
{
	return Bag.add(newEntry);
}

template<class ItemType>
bool Set<ItemType>::remove(const ItemType& anEntry)
{
	return Bag.remove(anEntry);
}
template<class ItemType>
bool Set<ItemType>::contains(const ItemType& anEntry) {

	return Bag.contains(anEntry);
}
template<class ItemType>
vector<ItemType> Set<ItemType>::toVector() const{
	return Bag.toVector();
}
#endif


//Main


#include<iostream>
#include "Set.h"

using namespace std;
int main()
{

	Set<int> set1;
	Set<int> set2;
	Set<int> set3;
	int selection;
	int element;
	do
	{

		cout << "1. add elements to set1\n";
		cout << "2. add elements to set2\n";
		cout << "3. remove an element from set1\n";
		cout << "4. remove an element from set2\n";
		cout << "5. do a union of set1 and set2 into set3\n";
		cout << "6. do an intersection of set1 and set2 into set3\n";
		cout << "7. print set1, set2, and set3\n";
		cout << "0. Quit\n";

		cin >> selection;

		switch (selection)
		{
		case 1:
			cout << "Add any number to set 1 (0 will quit the program): ";
			cin >> element;
			set1.add(element);
			break;
		case 2:
			cout << "Add any number to set 2 (0 will quit the program): ";
			cin >> element;
			set2.add(element);
			break;
		case 3:
			cout << "Remove a number within set 1: ";
			cin >> element;
			set1.remove(element);
			break;
		case 4:
			cout << "Remove a number within set 2: ";
			cin >> element;
			set2.remove(element);
			break;
		case 5:
			set3 = set1 + set2;
			break;
		case 6:
			set3 = set1 - set2;
			break;
		case 7:
			cout << "Set 1: " << set1 << endl;
			cout << "Set 2: " << set2 << endl;
			cout << "Set 3: " << set3 << endl;
			break;
		case 0:
			cout << "Exiting Program.\n";
			break;
		default:
			break;
	}

	} while (selection != 0);
	system("pause");
	return 0;
}

[jonnin]

I don't see anything right of but your + (union) operation seems funky.

wouldn't it just be

copy = set a
for all of set b:
if setb.item not in copy, add it to copy, else do nothing

return copy