From: "Eric I." <rubytraining@...>
Date: 2008-09-05T14:29:14+09:00
Subject: Re: Need a 40 LOC (ignoring comments) to be shorter -- suggestions 	wanted

On Sep 4, 9:40 pm, RichardOnRails
<RichardDummyMailbox58...@uscomputergurus.com> wrote:
> Hi All,
>
> My middle-school granddaughter posed the following challenge to me:
>
> Within 10 minutes, Use the digits 3 to 7 in any order
> to form a three-digit multiplicand and a two-digit multiplier
> such that their product is minimal.
>
> Out of curiosity as to whether my guess was right,
> and with a view toward eliciting an interest in her
> for Ruby programming,  I wrote the program posted athttp://www.pastie.org/266447
>
> The program reveals that I was wrong, but it took me about 40 lines of
> code,
> ignoring comments.  That would probably overwhelm her.  I was hoping
> that
> the code could be condensed with Ruby-isms.  BTW, I left some put’s in
> there
> intended to give her a sense of the programs functionality.
>
> Any ideas/suggestions?


Here's one solution that requires the 'permutation' gem:

====

require 'rubygems'
require 'permutation'

perm = Permutation.for((3..7).to_a)

min_product = 10**5
min_values = nil

perm.map do |p|
  a = p.project
  v1 = a[0, 3].to_s.to_i
  v2 = a[3, 2].to_s.to_i
  product = v1 * v2
  if product < min_product
    min_product = product
    min_values = [v1, v2]
  end
end

puts "#{min_values.first} * #{min_values.last} = #{min_product}"

====

Eric

====

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