From: Pablo Bianciotto <bianciottopablo@...>
Date: 2013-04-13T00:39:16+09:00
Subject: Re: Looking for a more elegant solution.

--001a11c1b6485eff0f04da2b976d
Content-Type: text/plain; charset=ISO-8859-1

Try the following:

1.upto(n).to_a.permutation(n).to_a.delete_if { |perm| perm.any? { |letter|
letter == perm[letter -1] } }


2013/4/12 Shaw xx <lists@ruby-forum.com>

> I'm new to ruby and working on such a problem:
>
> There n numbered letters and n numbered envelops.  The letter x can't be
> put into the envelop x. What I want is to print out all the possible
> cases.
>
> [letter(x1), letter(x2), ... , letter(xn)]
>       |            |                  |
>  envelop1, envelop2, ... ,  envelop n
>
> The index of Array + 1 ---> the number of the envelop
>
> The element of Array ---> the number of the letter
>
> Input:      n = 3.
> Output:    [1, 3, 2], [2, 3, 1]
>
> Input:     n = 4.
> Output:   [2, 1, 4, 3], [2, 3, 4, 1], [2, 4, 1, 3], [3, 1, 4, 2],
>           [3, 4, 1, 2], [3, 4, 2, 1], [4, 1, 2, 3], [4, 3, 1, 2],
>           [4, 3, 2, 1]
>
> Here is my code:
> -----------------------
> $nums = []
>
> def f( already, n, times )
>   if n > times
>     $nums << already.dup
>     return
>   else
>     1.upto(times) do |i|
>       next if ((already.include? i) || n == i)
>       already << i
>       f( already, n+1, times )
>       already.pop
>     end
>   end
> end
> ------------------------
>
> Sorry for my poor English. Thank you very much.
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

--001a11c1b6485eff0f04da2b976d
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Try the following:<br><br>1.upto(n).to_a.permutation(n).to=
_a.delete_if { |perm| perm.any? { |letter| letter =3D=3D perm[letter -1] } =
}<br></div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">20=
13/4/12 Shaw xx <span dir=3D"ltr">&lt;<a href=3D"mailto:lists@ruby-forum.co=
m" target=3D"_blank">lists@ruby-forum.com</a>&gt;</span><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">I&#39;m new to ruby and working on such a pr=
oblem:<br>
<br>
There n numbered letters and n numbered envelops. =A0The letter x can&#39;t=
 be<br>
put into the envelop x. What I want is to print out all the possible<br>
cases.<br>
<br>
[letter(x1), letter(x2), ... , letter(xn)]<br>
=A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|=
<br>
=A0envelop1, envelop2, ... , =A0envelop n<br>
<br>
The index of Array + 1 ---&gt; the number of the envelop<br>
<br>
The element of Array ---&gt; the number of the letter<br>
<br>
Input: =A0 =A0 =A0n =3D 3.<br>
Output: =A0 =A0[1, 3, 2], [2, 3, 1]<br>
<br>
Input: =A0 =A0 n =3D 4.<br>
Output: =A0 [2, 1, 4, 3], [2, 3, 4, 1], [2, 4, 1, 3], [3, 1, 4, 2],<br>
=A0 =A0 =A0 =A0 =A0 [3, 4, 1, 2], [3, 4, 2, 1], [4, 1, 2, 3], [4, 3, 1, 2],=
<br>
=A0 =A0 =A0 =A0 =A0 [4, 3, 2, 1]<br>
<br>
Here is my code:<br>
-----------------------<br>
$nums =3D []<br>
<br>
def f( already, n, times )<br>
=A0 if n &gt; times<br>
=A0 =A0 $nums &lt;&lt; already.dup<br>
=A0 =A0 return<br>
=A0 else<br>
=A0 =A0 1.upto(times) do |i|<br>
=A0 =A0 =A0 next if ((already.include? i) || n =3D=3D i)<br>
=A0 =A0 =A0 already &lt;&lt; i<br>
=A0 =A0 =A0 f( already, n+1, times )<br>
=A0 =A0 =A0 already.pop<br>
=A0 =A0 end<br>
=A0 end<br>
end<br>
------------------------<br>
<br>
Sorry for my poor English. Thank you very much.<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
--<br>
Posted via <a href=3D"http://www.ruby-forum.com/" target=3D"_blank">http://=
www.ruby-forum.com/</a>.<br>
<br>
</font></span></blockquote></div><br></div>

--001a11c1b6485eff0f04da2b976d--