Array Diagonals Reversion?

[ieatcalculus]

Challenging us on the last day of class with the ultimate question, my professor gave us this problem.
It's nearing midnight (11:55), and I've completely given up hope.

This is the problem:

Reverse the diagonals of a square 2-D array for any size square array.

For example,
9 8 7
6 5 4
3 2 1

would become:

1 8 3
6 5 4
7 2 9

Likewise, the array

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16


would become:
12 2 3 14

5 11 10 8

9 7 16 12

4 14 15 1

Exactly what sort of C++ wonder would I have to use to solve this problem?
Just any hint would be helpful and much appreciated (:

[laserlight]

What have you tried?

[ieatcalculus]

I have no idea how to even start. It's past midnight now

I just need a hint; I obviously have to write the program myself.

[laserlight]

I would imagine that you have to use a loop or two to swap diagonal entries.

You can start with a simpler problem: print the diagonal entries of a square array of arbitrary order.