From: James Edward Gray II <james@...>
Date: 2007-04-09T11:11:34+09:00
Subject: Fwd: Please Forward: Ruby Quiz Submission

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Begin forwarded message:

> From: Dennis Frommknecht <dennis@frommknecht.net>
> Date: April 8, 2007 12:26:42 PM CDT
> To: submission@rubyquiz.com
> Subject: Please Forward: Ruby Quiz Submission
>
> Hi,
>
> here is a solution for quiz number 119.
> As I'm not subscribed to the mailing list, i hope you can forward it.
>
> Thanks,
>
> Dennis Frommknecht
>
>

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#!/usr/bin/env ruby -W

# This solution uses 3 nested loops to divide the 
# numbers into 4 groups (using regular expressions). 
# Then the 3 allowed combinations of plus and minus
# are inserted between the groups.
# Finally the result is calculated using eval

NUMBERS = "123456789"
CORRECT_RES = 100
OPS = [['+', '-', '-'],
       ['-', '+', '-'],
       ['-', '-', '+']]

num_of_ops = OPS[0].length
equ_counter = 0

1.upto(NUMBERS.length - num_of_ops) do |i|
1.upto(NUMBERS.length - num_of_ops - i + 1) do |j|
1.upto(NUMBERS.length - num_of_ops - i + 1 - j + 1) do |k|
  if NUMBERS.match(/(\d{#{i}})(\d{#{j}})(\d{#{k}})(\d+)/) then
    OPS.each do |o|
      command = "#{$1} #{o[0]} #{$2} #{o[1]} #{$3} #{o[2]} #{$4}"
      res = eval command
      equ_counter += 1      
      puts "*" * 15 if res == CORRECT_RES
      puts "#{command} = #{res}"
      puts "*" * 15 if res == CORRECT_RES
    end
  end
end
end
end

puts "#{equ_counter} possible equations tested"

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