Recombinate two complex attributes into new object

I want to recombine a (complex) member attribute of two agents and put it in a new agent. It's a vector of numbers, every second value is taken from agent1, the rest from agent2. The problem is, I want to be able to exchange the implementation of my numberList, maybe another numberListInt2 using integers or like in my example using floats:

#include <vector>

using namespace std;

class NumberList {
};

class NumberListInt : public NumberList {
    vector<int>  number_list {1,2,3};
};

class NumberListFloat : public NumberList {
    vector<float>  number_list  {1.2f,2.5f,30.0f};
};

class Agent {
    NumberList* numbers;
    public:
        Agent();
        Agent(NumberList* numbers) {
            numbers = numberList*
        }
        ~Agent() {
            delete numbers;
        }
        NumberList* recombine(Agent& other) {
            NumberList* new_number_list;
            if(true) // a boolean config value
                new_number_list = new NumberListInt();
            else
                new_number_list = new NumberListFloat();

            for(unsigned int i=0;i<3;i++) {
                if(i%2)
                    new_number_list[i] = other.get_number_list()[i];
                else
                    new_number_list[i] = numbers[i];
            }
            return new_number_list;
        }

        NumberList* get_number_list() {
            return numbers;
        }
};

int main ()
{
    Agent agent;
    Agent agent2;
    Agent agent3(agent.recombine(agent2));
    return 0;
}

My questions:

1. How to implement the operator [] of NumberList?
2. Is there a better way than using a pointer for the polymorphism?
3. Do I free the memory correctly?

Thanks in advice!