Please help with displaying 2D array

[depecheSoul]

I got assigment at my school to display 2D array like this:

This is default array:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

Now I have to print the default array like this:

1 2 6 7
3 5 8 13
4 9 12 14
10 11 15 16

I have tried some codes to do it myself but i had no succes.

Please can you give information what algorithm to use, to make this program work:

Thank you very much!!!