How to define a 2D array in C++ and STL without memory manipulation?

Question

There are several ways to define a 2D array in C++ and STL without memory manipulation, and the following codes illustrate two different methods:

int main () 
{
         


        

Answer 1

A common pattern is encapsulating the 2D array inside a class that offers the appropriate interface. In that case, you can use other internal representations, like for example a single vector of rows*cols elements. The interface (usually operator()(int,int) will map the coordinates from the caller to a position in the linear vector.

The advantage is that it has dynamic allocation, but a single allocation (unlike the std::vector> where each vector must acquire it's own memory) and in a single block providing locality of data.