How do you dynamically allocate a matrix?

Question

How do you dynamically allocate a 2D matrix in C++? I have tried based on what I already know:

#include 

int main(){
    int rows;
    int c         


        

Answer 1

or you can just allocate a 1D array but reference elements in a 2D fashion:

to address row 2, column 3 (top left corner is row 0, column 0):

arr[2 * MATRIX_WIDTH + 3]

where MATRIX_WIDTH is the number of elements in a row.