c++ declare an array of arrays without know the size

Question

I must declare an array of arrays or multidimensional array without know the size. I want to do something similar that I do in this cases with simple arrays:

Answer 1

If you care, you can have a little bit more convenience by have a helper

template 
struct C3DArray
{
    vector>> m;
    C3DArray(int size_x, int size_y, int size_z)
        : m(make(T(), size_z, size_y, size_x))
    { }

    template  static std::vector make(U v, size_t n) {
        return { n, std::move(v) };
    }

    template  static auto make(U v, size_t n, Dim... other)
        -> std::vector {
        return { n, make(v, other...) };
    }
};

This uses variadics. Use it like this:

C3DArray arr(3,4,20);