Ruby Quiz #148

ruby-talk
1

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

2

I've looked at a lot of solutions for this quiz today and I have to say
I like yours the most. Good work :slight_smile:

···

--
Posted via http://www.ruby-forum.com/.

3

This is incorrect:

postfix = 3 5 * 5 8 * /
infix = 3 * 5 / 5 * 8

It should be
infix = 3 * 5 / (5 * 8)

--Ken

···

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

--
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/

4

Since there was no name specified, I think all solvers should assume he was talking to you. :wink:

James Edward Gray II

···

On Dec 2, 2007, at 9:17 PM, Michael Boutros wrote:

I've looked at a lot of solutions for this quiz today and I have to say
I like yours the most. Good work :slight_smile:

5

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/~kbloom1/&gt;