How do I define a Vector of Vectors in C++?

Question

I would like to create a vector, and in each cell of this vector I would like to keep another vector which will contain a certain struct I defined. How am I supposed to do that? Am I supposed to define a pointer from each cell in the main vector to each of the other vectors (containing the structs I defined)? Am I supposed to access the memory where the vector is created using a pointer?

This is how I thought of doing it but I am honestly not really sure what I am doing:

vector<*vector> *vec = new vector<vector>

NOTE: I am a beginner in C++ and new to programming in general so go easy on me on this one fellas.

Thanks a lot

Answer 1

The general rule is don't use pointers (and dynamic allocation) unless you need to. So you can simply do this:

std::vector<std::vector<your_struct> > vector_of_vectors;

Answer 2

Just like you would instantiate a vector of anything:

std::vector<std::vector<MyType>> v;

Pointers have nothing to do with it. You use a vector of pointers if and only if you need a vector of pointers.

Answer 3

You don't need pointers, you can just use

std::vector<std::vector<int>> vec( 100 ); // create a vector of 100 vector<int> 
vec[42].push_back(1764); // add an element to the 43rd vector<int>