c++ - dynamically allocating 3d array

Question

I'm a little confused about dynamically allocating a 3d array. Right now, I'm just allocating one big block of memory like so:

int height = 10;
int depth = 20;
int width = 5;

int* arr;
arr = new int[height * width * depth];

Now I'd like to change a value in the 3D array, say:

//arr[depth][width][height]
arr[6][3][7] = 4;

However, I can't use the above code to change the value. How can I use a single index to access the element at position depth = 6, width = 3, height = 7?

arr[?] = 4;

Is there a better way to dynamically allocate a 3D array?

Answer 1

C inclined way of doing this is:

int ***arr = new int**[X];
for (i = 0; i < z_size; ++i) {
  arr[i] = new int*[Y];
  for (j = 0; j < WIDTH; ++j)
    arr[i][j] = new int[Z];
}