Matricies

2d arrays yayayaya

int array_2d[2][3]; // 2 rows and 3 columns.

• In memory it’s read left to right line by line

Offset formula

$\text{Offset = (column \#}\times \text{column size})+\text{row \#}$

Syntax

You cannot declare a 2D array w/o a set size:

int someMatrix[][]; // NOT allowed! Will not compile
int* someMatrix; // Allowed!

Example

char array[2][3] = {
	{'A', 'B', 'C'},
	{'D', 'E', 'F'},
};

A	B	C
D	E	F
In memory would just be A, B, C, D, E, F.

I think you could technically do something like

int arr[2][3];
 
*(*arr+3) = 4; // This would be the second row, first column!? !?!?!?

Note!

For the above code, there is a difference between *(arr + 3) = 4 and *(*arr + 3) = 4

The top example doesn’t work. Why? Because we cannot “manipulate arrays” as it says by the compiler. What does that mean? Well consider matrix[2][3] and array[i] = *(array + i) Using the literal definition of [], we see matrix[2][3] = *(matrix + 2)[3]. Clearly *(matrix + 2) is still an array as we can index [3] from it. That should explain why it gives the error: *(arr + 3) is