Re: noob question - pattern matching

On Fri, Aug 12, 2011 at 12:31 PM, Jesper Brandt <[e-mail]> wrote:

> I have a list of 22000 8 digit numbers. Im looking for a number which is
> the "best" from a defined set of patterns.
>
> a pattern could be "abababab" givng a score of 10, and another would be
> "abab" giving a score of 5. Patterns could also be specific digits, so
> another pattern defining "a0b0" - giving 7 points would mean that it
> would only match if there is zeroes in the number such as 10203040 (with
> all the above rules it would give 21 points).
>
> This way the number 52525252 would give a score of 25 and the number
> 52526262 would give the score of 10.
>
> do anybody have a good idea on how to make such a scoring in ruby?
>
> I'm sorry - but im a bit of a noob regarding ruby, but thought it would
> be a good project to get a better virew on the language:-)
> Regards
>
> JB
>
>
#!/usr/bin/env ruby

PATTERNS = {
  /(\d)(\d)\1\2\1\2\1\2/ => 10, # abababab (aaaaaaaa too though)
  /(\d)(\d)\1\2/         => 5,  # abab (aaaa too though)
  /\d0\d0/               => 7   # a0b0 (a0a0 too though)
}

NUMBERS = %w{
  12345678
  00000000
  12121212
  01020102
  23240102
}

def score(number)
  PATTERNS.reduce(0) do |score, entry|
    entry.first =~ number ? score + entry.last : score
  end
end

puts NUMBERS.map { |n| "#{n} => #{score(n)}" }.join("\n")

--
There are several things you didn't specify fully (such as whether the
shorter 4-digit patterns can match anywhere in a number or whether they
should be anchored to the beginning/end of the number, etc.) but you could
easily adjust the patterns and/or logic to suit. Additionally, if a pattern
was too complex to be specified using a regular expression, you could let
the PATTERNS hash have Regexp _or_ lambda instances and update the #score
method to detect which each pattern entry is and do the right thing.

-- 
Kendall Gifford
[e-mail]