Vector of List of Object Manipulation

#include <iostream>
#include <list>
#include <vector>

using namespace std;

class portfolio {
    public:
        portfolio() {
            _id = 0;
            gain_ = 0; 
        }
        
        portfolio(int id, int gain) {
            _id = id;
            gain_ = gain; 
        }
        
        portfolio(const portfolio& obj) {
            _id = obj._id;
            gain_ = obj.gain_;
        }
        
        int _id;
        int get_gain() const {
            return gain_;
        }
        void set_gain(int gain) {
            gain_ = gain;
        }
        
    private:
        int gain_;
};

int main()
{
    vector<list<portfolio>> rothschild;
    
    list<portfolio> cow;
    list<portfolio> star;
    list<portfolio> dog;
    list<portfolio> que;
    
    rothschild.push_back(cow);
    rothschild.push_back(star);
    rothschild.push_back(dog);
    rothschild.push_back(que);
    
    for(int i = 1; i < 10; i++) {
        int gain = 5;
        portfolio cowCompany(i, gain);
        rothschild[0].push_back(cowCompany);
        
        gain = 10;
        portfolio starCompany(i*10, gain);
        rothschild[1].push_back(starCompany);
        
        gain = 1;
        portfolio dogCompany(i*100, gain);
        rothschild[2].push_back(dogCompany);
        
        gain = 3;
        portfolio queCompany(i*1000, gain);
        rothschild[3].push_back(queCompany);
    }
    
    cout << "Finish Constructing" << endl;
    
    /*-Reverse Range queCompany-*/
    list<portfolio> tempRev;
    list<portfolio> tempRemain;
    int id = 3;
    //--Reverse at index 4-7
    int start = 3;
    int end = 6;
    list<portfolio>::iterator fit = rothschild[id].begin();
    list<portfolio>::iterator bit = rothschild[id].begin();
    advance(fit, start);
    advance(bit, end);
    cout << "Slicing" << endl;
    rothschild[id].splice(tempRemain.begin(), rothschild[id], bit, rothschild[id].end());
    rothschild[id].splice(tempRev.begin(), rothschild[id], fit, rothschild[id].end());
    tempRev.reverse();
    rothschild[id].splice(rothschild[id].end(), tempRev);
    rothschild[id].splice(rothschild[id].end(), tempRemain);
    
    /*-Reorder Cow-*/
    list<portfolio> tempOdd;
    list<portfolio> tempEven;
    int size = rothschild[0].size();
    for(int i = 0; i < size; i++) {
        portfolio obj;
        obj = rothschild[0].front();
        rothschild[0].pop_front();
        
        if(obj._id % 2 == 0) {
            //Even 
            tempEven.push_back(obj);
        } else {
            tempOdd.push_back(obj);
        }
    }
    rothschild[0].splice(rothschild[0].begin(), tempEven);
    rothschild[0].splice(rothschild[0].end(), tempOdd);
    
    /*-Remove Odd dogCompany-*/
    rothschild[2].remove_if([](portfolio & obj) {return ((obj._id/100)%2) == 1;});
    
    
    
    for(auto &i : rothschild) {
        
        for(auto &j : i){
            cout << j._id << endl;
        }
    }
    
    cout << "Temp: " << endl;
    for(auto &i : tempRev) {
        cout << i._id << endl;
    }

    return 0;
}