Subj : Re: Algorithm to generate permutation for a non sequential single array
To   : comp.programming
From : cri
Date : Fri Jul 01 2005 06:20 pm

On 1 Jul 2005 09:07:12 -0700, "mmarin1m@hotmail.com"
<mmarin1m@hotmail.com> wrote:

>Hi all,
>
>I'm looking for an algorithm that would generate all permutations for a
>given non sequential list. As an example:
>
>Given the list 125, 126, 5, 88 and 33, all permutations must be
>generated in that sequence.
>
>The perfect algorithm would yields the following matrix:
>
>125, 126, 5, 88, 33
>125, 126, 5, 88
>126, 5, 88, 33
>125, 126, 5
>125, 126, 88
>125, 126, 33
>125, 5, 88
>125, 5, 33
>125, 88, 33
>126, 5, 88
>126, 5, 33
>126, 88, 33
>5, 88, 33
>125, 126
>125, 5
>125, 88
>125, 33
>126, 5
>126, 88
>126, 33
>5, 88
>5, 33
>88, 33
>125
>126
>5
>88
>33
>
>Sorry about the length of this post.
>
>The fact that the numbers are non sequential is irrelevant. What
>matters is that 126 should never appears before 125, etc, etc.
>
>Thank you in advance,

What you are asking for appears to be to list all of the sublists of
your original list while retaining the original order.  There will be
2**n of these (counting the empty list).  Map the problem into bit
strings of length n, using 1's to mark elements present.  For n=3

S = {a,b,c}

111 -> a,b,c
110 -> a,b
101 -> a,c
011 -> b,c
100 -> a
010 -> b
001 -> c
000 ->

Is this what you want?



Richard Harter, cri@tiac.net
http://home.tiac.net/~cri, http://www.varinoma.com
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It's the only planet with chocolate.

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