Re: Randomly outputting an array

In article <Pine.LNX.4.60-041.0607161411410.6121
@unix43.andrew.cmu.edu>, ajonospam@xxxxxxxxxxxxxx says...

Picking N pairs uniformly at random and swapping them will definitely
not shuffle the array, since there are (N^2)^N = N^(2N) ways to pick
N pairs, and N! ways to shuffle the array, and N^(2N) is generally not
a multiple of N!.

However, if you carefully pick those N pairs so that the first swap
swaps a random element into position 1, the second swap swaps a random
element /from those that remain/ into position 2, and so on, then that's
the "52-card pickup" algorithm, and it works fine. It's all in /which/
N pairs you swap.

You're right, my method doesn't work. I can't quite see what is
logically wrong with it, but if it makes n^n possible results, n! isn't
going to divide exactly into it.

- Gerry Quinn
.

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