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MathGroup Archive 2006

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Re: Word permutations - frustrated by lists.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71720] Re: Word permutations - frustrated by lists.
  • From: Peter Pein <petsie at dordos.net>
  • Date: Mon, 27 Nov 2006 04:04:53 -0500 (EST)
  • References: <ekbrks$jga$1@smc.vnet.net>

wooks schrieb:
> Hello. Am relatively new with Mathematica.
> 
> I seem to have a general problem with results that look right but for
> embedded lists. Here is an example of my problem. This is supposed to
> be a algorithm to generate all permutations of a string. T
> 
> Clear[arrangements]
> arrangements[str_String /; StringLength[str] == 1] := {str};
> arrangements[str_String] := (Prepend[arrangements[StringJoin[
>     Rest[#]]]], First[#]) & /@
>        NestList[RotateRight, Characters[str], StringLength[str] - 1];
> arrangements["dear"]
> 
> PS This is not homework. I'm rewriting some examples from another
> programming book as as practice  for Mathematica.
> 
What about
In[1]:= Apply[StringJoin, Permutations[Characters["dear"]], {1}]
Out[1]=
{"dear", "dera", "daer", "dare", "drea", "drae", "edar", "edra", "eadr",
"eard", "erda", "erad", "ader", "adre", "aedr", "aerd", "arde", "ared",
"rdea", "rdae", "reda", "read", "rade", "raed"}

?


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