A Challenge For Prog

No, I'm not a student looking to get my program written for me.
I'm just trying to find the most optimized solution to a problem, and at the same time it makes a decent challenge for /prog/.

The problem :-

You have a set of doubly-linked classes. (Yes this is C++).
Each class contains an int of any value.

You must rearrange the links so that every possible combination of numbers is displayed to the console screen.

E.g
class 1 contains 1, 2 contains 2, 3 contains 3.
So it's 123.

Now the program needs to have this output:
123
132
213
231
321
312

DOES /PROG/ RISE TO THE CHALLENGE?