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

If you know the elements beforehand then you could just do

int arr[2][3] = {{1,2, 3}, {4, 5, 6}};

This should be more efficient than method1 and method2. Using vectors, you are not doing memory manipulation yourself, but the vector implementation will probably use a dynamically allocated array.