Well, there's more to an algorithm than its run-time complexity. You also need to prove the algorithm is correct. That is in this case show that the resulting array is a permutation of the original one (fairly trivial), and that each permutation has an equal chance of being selected (a bit more work, but still not to hard, if you can assume your random generator produces real random numbers).

For details, see the Knuth reference I made in another post in this thread.

Abigail