Re: Algorithm to generate permutation for a non sequential single array
- From: Jon Harrop <usenet@xxxxxxxxxxxxxx>
- Date: Tue, 05 Jul 2005 18:24:26 +0100
mmarin1m@xxxxxxxxxxx wrote:
> I'm looking for an algorithm that would generate all permutations for a
> given non sequential list.
As others have already said, you are asking for the list of all subsets,
nothing to do with permutations.
The following 3-line OCaml function does this:
let rec subsets = function
[] -> [[]]
| h :: t -> (fun t -> List.map (fun t -> h :: t) t @ t) (subsets t);;
For example:
# let rec subsets = function
[] -> [[]]
| h :: t -> (fun t -> List.map (fun t -> h :: t) t @ t) (subsets t);;
val subsets : 'a list -> 'a list list = <fun>
# subsets [125; 126; 5; 88; 33];;
- : int list list =
[[125; 126; 5; 88; 33]; [125; 126; 5; 88]; [125; 126; 5; 33]; [125; 126; 5];
[125; 126; 88; 33]; [125; 126; 88]; [125; 126; 33]; [125; 126];
[125; 5; 88; 33]; [125; 5; 88]; [125; 5; 33]; [125; 5]; [125; 88; 33];
[125; 88]; [125; 33]; [125]; [126; 5; 88; 33]; [126; 5; 88]; [126; 5; 33];
[126; 5]; [126; 88; 33]; [126; 88]; [126; 33]; [126]; [5; 88; 33]; [5; 88];
[5; 33]; [5]; [88; 33]; [88]; [33]; []]
--
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com
.
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- From: mmarin1m@xxxxxxxxxxx
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