From: Dave Pederson <dave.pederson.ruby@...>
Date: 2007-12-03T16:46:07+09:00
Subject: Re: Fwd: Ruby Quiz #148

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Thanks for pointing that out.  I was trying to minimize parentheses...looks
like i kinda hurried though it.  Anyways, here was my first solution (minus
the bonus points):

#!/usr/bin/env ruby

op = %w{ + - * / }
postfixes = ["2 3 5 + *",
             "1 56 35 + 16 9 - / +",
             "56 34 213.7 + * 678 -",
             "5 9 * 8 7 4 6 + * 2 1 3 * + * + *",
             "3 5 * 5 8 * /"]

postfixes.each do |postfix|
  stack = []
  postfix.split.each do |c|
    unless op.include? c
      stack.push(c)
    else
      second, first = stack.pop, stack.pop
      stack.push "( #{first} #{c} #{second} )"
    end
  end
  puts "postfix = #{postfix}"
  puts "infix = #{stack.pop}"
  puts
end



On Dec 2, 2007 8:40 PM, Ken Bloom <kbloom@gmail.com> wrote:

> On Sun, 02 Dec 2007 21:47:29 -0500, Dave Pederson wrote:
>
> > Note:  parts of this message were removed by the gateway to make it a
> > legal Usenet post.
> >
> > Solution to quiz #148.
> > Thanks,
> >
> > -Dave
> > ---------- Forwarded message ---------- From: Dave Pederson
> > <dave.pederson.ruby@gmail.com> Date: Nov 30, 2007 7:26 PM
> > Subject: Ruby Quiz #148
> > To: dave.pederson.ruby@gmail.com
> >
> >
> > #!/usr/bin/env ruby
> >
> > op = %w{ + - / * }
> > pm = %w{ + - }
> >
> > postfixes = ["2 3 5 + *",
> >              "1 56 35 + 16 9 - / +",
> >              "56 34 213.7 + * 678 -",
> >              "5 9 * 8 7 4 6 + * 2 1 3 * + * + *"]
> >
> > puts
> > postfixes.each do |postfix|
> >   stack = []
> >   postfix.split.each do |c|
> >     if op.include?(c)
> >       second, first = stack.pop, stack.pop
> >       if pm.include?(c)
> >         stack.push "(#{first} #{c} #{second})"
> >       else
> >         stack.push "#{first} #{c} #{second}"
> >       end
> >     else
> >       stack.push(c)
> >     end
> >   end
> >   infix = stack.pop
> >   if (infix[0] == 40 && infix[infix.size-1] == 41)
> >     infix = infix[1, infix.size-2]
> >   end
> >   puts "postfix = #{postfix}"
> >   puts "infix = #{infix}"
> >   puts
> > end
>
> This is incorrect:
>
> postfix = 3 5 * 5 8 * /
> infix = 3 * 5 / 5 * 8
>
> It should be
> infix = 3 * 5 / (5 * 8)
>
> --Ken
>
> --
> Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
> Department of Computer Science. Illinois Institute of Technology.
> http://www.iit.edu/~kbloom1/ <http://www.iit.edu/%7Ekbloom1/>
>
>

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