Question

I’ve found that using a vector is the best way to achieve what I need to do, however I now need some clarification.

I need to generate a multidimensional array within a function in an external CPP, then make this available within main.

main.cpp

// include vector, using namespace etc.
function(2, 4);

// how to access vector elements here - vectorname[2][4]->classvar;  ? 

vectors.cpp

void function(value1, value2){
// class def
int value1 = value1;
int value2 = value2;
 vector<int>(value1)<vector<Class>(value2) vectorname>; // incorrect syntax? or new * vector ?

return vectorname; // ?
}

Answer 1

The syntax with vector requires a little getting used to. A 2D vector of int looks like this:

vector<vector<int> > myVector;

If you would like to set specific dimensions, use constructors that take size:

vector<vector<int> > myVector(10, vector<int>(5));

This produces a 10x5 vector of zeros. You can do this

vector<vector<int> > myVector(10, vector<int>(5, -1));

to provide initial values for your elements (-1 in this case).

As a rule of thumb, you want your vectors passed by reference and returned by value.