[ot] Re: [PD] permutations

[Orm Finnendahl]

Hi Krzysztof,

you're absolutely right. Blame on me. Permutations are distinct from
combinations in being ordered and having the same number of elements
(in difference to variations being ordered subsets). That's what
happens if you want to be smart... In my mail it should say "the
period of one permutation, continously reapplied to itself...".

BTW, my mail somehow got mixed up with a former one, I wrote before I
had a glance at the code. The external I was talking about, maps index
numbers (ranging from 0 to ((n factorial) -1)), received as integer in
the inlet, into a one-to-one correspondance to all possible
permutations. With this permutation set, any list received in the
inlet got reordered according to it.

I don't remember, how I did the algorithm, which directly calculates a
permutation from an integer. I remember finding it quite
challenging. But go have a look :-)

Yours,
Orm


Am Freitag, den 25. Januar 2002 um 14:43:38 Uhr (+0100) schrieb Krzysztof Czaja:
> hi Orm,
> 
> this is from MathWorld:
> 
> Permutation: The rearrangement of elements in an ordered list S
> into a one-to-one correspondence with S itself, also called an
> "arrangement number" or "order."  The number of permutations on
> a set of elements is given by n! (n factorial).
> 
> Combination: The number of ways of picking k _unordered_ outcomes
> from n possibilities.  Also known as the binomial coefficient or
> choice number [...] For example [for n==4, k==2] there are 6
> combinations on {1,2,3,4}, namely {1,2}, {1,3}, {1,4}, {2,3},
> {2,4}, and {3,4}.
> 
> yKzzsofrt
> 
> Orm Finnendahl wrote:
> > 
> > hi Krzyzstof,
> ...