Random Unique Lists of 12 Numbers

[baja_yu]

I might be a bit rusty, but I think that the n^k forumula is for permutations without repetition. For combinations n! / k!(n-k)! is also correct. Permutations return a list of sequences, whereas combinations return a list of sets. The difference being that in sequences the order of items matters (1, 2, 3) is different from (1, 3, 2), whereas with combinations the order of elements is not important so {1, 2, 3} is the same as {1, 3, 2}, {2, 3, 1} etc, thus the much lesser count of combinations than permutations.

But like you said, much clarification is needed on the problem. Still, as you illustrated the size point later which I didn't think of, even with the best possible scenario of all those, the size would still be huge.

EDIT: It really depends on the missing details, and the real purpose of this. If you just want to test the computational power/speed of the CPU, you might be better off looking at some ready made software like SuperPI http://en.wikipedia.org/wiki/Super_PI.

EDIT2: I was wrong with my original formula. n^k is for permutations with repetition, and n! / (n-k)! is without repetitions. Combinations without repetition on the other hand are n! / k! (n-k)!