From: david karapetyan <dkarapetyan@...>
Date: 2007-07-15T17:23:45+09:00
Subject: Re: xkcd and ugly code

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This is basically a backtracking problem and the best way to deal with such
problems I think is continuations.

On 7/15/07, Sharon Phillips <phillipsds@yahoo.co.uk> wrote:
>
> Hi,
>
> I read this xkcd strip the other day (http://www.xkcd.com/c287.html)
> and, of course, had to solve it. So I whipped up a quick bit of Ruby
> code that gave me the answers. Took about 5 minutes and then I was
> happy. Except I wasn't, because I looked at what I'd written. Ugly
> and not dry at all, sopping wet even; basically six nested loops.
> I'll try to reproduce it below.
>
> Trouble is, I then spend the best part of an afternoon (don't tell my
> boss ;-) trying to solve it elegantly, but couldn't. I did come up
> with other ways that worked, but they were pretty cumbersome and slow.
>
> There has to be a 'ruby way' to do this. Any suggestions?
>
> Cheers,
> Dave
>
> here's a rough approximation of the code I wrote:
>
> menu= [2.15, 2.75, 3.35, 3.55, 4.20, 5.80]
> target= 15.05
> 0.upto(target/menu[0].to_i) do |a|
>    0.upto(target/menu[1].to_i) do |b|
>      0.upto(target/menu[2].to_i) do |c|
>        0.upto(target/menu[3].to_i) do |d|
>          0.upto(target/menu[4].to_i) do |e|
>            0.upto(target/menu[5].to_i) do |f|
>              if ((total= a*menu[0] +
>                b*menu[1] +
>                c*menu[2] +
>                d*menu[3] +
>                e*menu[4] +
>                f*menu[5]) - target).abs<0.01 then
>                puts "\n#{a} * $#{menu[0]}"
>                puts "#{b} * $#{menu[1]}"
>                puts "#{c} * $#{menu[2]}"
>                puts "#{d} * $#{menu[3]}"
>                puts "#{e} * $#{menu[4]}"
>                puts "#{f} * $#{menu[5]}"
>                puts "---------------\n    $#{total}"
>              end
>            end
>          end
>        end
>      end
>    end
> end
>
>

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