#include <iostream>
#include <vector>

typedef std::vector<double> reals_list;

int main()
{
    std::vector<reals_list> list_of_lists;

    list_of_lists.push_back({20.0, 20.0, 0.0});
    list_of_lists.push_back({36.0, 150.0, 0.0});
    list_of_lists.push_back({200.0, 130.0, 0.0});
    list_of_lists.push_back({215.0, 20.0, 0.0});

    std::cout << list_of_lists[3][0]
        << ", " << list_of_lists[3][1]
        << ", " << list_of_lists[3][2] << std::endl;
}

#include <iostream>
#include <vector>

struct Vector3 {
    double x, y, z;
};

int main()
{
    std::vector<Vector3> list_of_lists;

    list_of_lists.push_back({20.0, 20.0, 0.0});
    list_of_lists.push_back({36.0, 150.0, 0.0});
    list_of_lists.push_back({200.0, 130.0, 0.0});
    list_of_lists.push_back({215.0, 20.0, 0.0});

    std::cout << list_of_lists[3].x
        << ", " << list_of_lists[3].y
        << ", " << list_of_lists[3].z << std::endl;
}