Access Multidimensional Array from C#

Question

This picture is taken from C# Intermediate, Multidimensional Array.
https://lecontent.sololearn.com/material-images/cf857db26cea415cb0219fe792e02267-2422.png

And this code is from the same module.

Is the figure wrong to shows how to access an element in multidimensional array?
In the code it use a comma (someNums[k, j]), but the figure is using 2 square brackets?

https://sololearn.com/compiler-playground/cs988EkPZh1h/?ref=app

Answer 1

int[][,] is confusing as heck. I would not put such a structure even in the intermediate course.

The multidim array with the comma syntax, is very much like a numpy array with rigid structure, like a matrix or cube.

The jagged array is like a list of lists where each element can have a different length (or maybe a tuple of tuples would be more appropriate, because C# arrays cannot change their sizes dynamically).

jagged example:
https://sololearn.com/compiler-playground/c0lBVngq2GAi/?ref=app

Answer 2

It seems I ask too fast.
A jagged array does use [][] to access the element.

In the last page of jagged array, it asked for a jagged array which has 8 elements, and each element is a 2D array.
int[][,] arr = new int[8][,]

Is it similar to a python numpy 3d array, but each inner array can have different size?

Answer 3

Thanks for remind me that array in C# is fixed size.