From: sanha lee <chdiary@...>
Date: 2005-12-13T01:46:24+09:00
Subject: Re: A question about recursive programming

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def all_sum(arr)
>  return arr if arr.length =3D=3D 1
>  temp =3D arr[-1]
# sorry about this, it should be return all_sum(arr[0...-1]) +
all_sum(arr[0...-1]).collect .....
# not all_sum(arr[1...-1]).collect.
>  return all_sum(arr[0...-1]) + all_sum(arr[1...-1]).collect {|i| i + temp=
}
> end

except that mistake, I can not see any difference between your code and
mine,
except that your code doesn't deal with the case where arr.length =3D=3D 1.
my result of all_sum([1, 2, 3, 4]) is this [1, 2, 3, 4, 6, 5, 7, 8, 10]
sorry if i am wrong, no offence.




On 12/12/05, dblack@wobblini.net <dblack@wobblini.net> wrote:
>
> Hi --
>
> On Tue, 13 Dec 2005, sanha lee wrote:
>
> > I think that it is better solution
> >
> > def all_sum(arr)
> >  return arr if arr.length =3D=3D 1
> >  temp =3D arr[-1]
> >  return all_sum(arr[0...-1]) + all_sum(arr[1...-1]).collect {|i| i +
> temp}
> > end
>
> I get a too-deep recursion with that too.  Here's another candidate:
>
>   def all_sum(arr)
>     case arr.size
>     when 1 then []
>     else arr[0..-2].map {|i| i + arr[-1]} + all_sum(arr[0..-2])
>     end
>   end
>
>   p all_sum([1,2,3,4])
>   =3D> [5, 6, 7, 4, 5, 3]
>
>
> David
>
> --
> David A. Black
> dblack@wobblini.net
>
> "Ruby for Rails", forthcoming from Manning Publications, April 2006!
>
>

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