2D Matrix allocation on heap in c++

Question

I am looking for a way to allocate a 2D (m x n) matrix on the heap where the elements are consecutive in memory. Currently I know of two ways to accomplish that:

First approach

int* M = new int[m * n];

• Pro: The size of M can by dynamically determined.
• Con: Indexing of M is a bit of a pain. (M[i * m + j])

Second approach

typedef int dim[2];
dim* M = new dim[n];

• Pro: Indexing of M is just how I want it to be.
• Con: The size of the first dimension (m) cannot be set dynamically.

Question

Is there a way to allocate a 2D matrix dynamically on the heap where I can index the elements with [i][j] and the memory allocation is consecutive?

I know it would make a lot of sense to use a class for that, but I am specifically looking for a way as described above.

Answer 1

You can try this

int** M = new int*[m];
int *M_data = new int[m*n];

for(int i=0; i< m; ++i) 
{
    M[i] = M_data + i * n;
}