From: Karsten Meier <discussionruby@...>
Date: 2004-07-19T02:47:11+09:00
Subject: Re: Another little algoritmic help needed...

There is a solution in the pleac cookbook, I have transferred it from 
the perl cookbook.
See http://pleac.sourceforge.net/pleac_ruby/arrays.html
Search for "program permute"
The second solution enables you to get the n-th permutation, so you can 
just increment a
integer each time you call the method, and you don't need to store any 
arrays.

Regards

Karsten Meier

Meino Christian Cramer wrote:
> Hi,
> 
> 
>  I want to produce from a give string all permutations of its
>  characters.
> 
>  Building all permutations of something is a typical recursive task.
>  But in this case I dont want a recursive solution because:
> 
> 
> 
>  1.) Each call of the according method should return only one
> 	 permutation of all possible permutations.
> 
> 
> 	 and
> 
> 
>  2.) Since the count of permutation rapidly grows with the count of
> 	 characters to permute I dont want to calculate all permutations
> 	 first and store them in a big BIG array.
> 	 Each new call that method should calculate just that next new
> 	 permutation. 
> 
> 
> 
>  I must confess: I have thought about that and did not find any
>  solution. Even the Sedgwick only offers a recursive solution.
> 
> 
>  Any ideas ?
> 
>  Ruby.use!
>  Meino 
> 
>