From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2007-09-26T17:18:58+09:00
Subject: Re: Detecting number ranges

On 9/26/07, Jay Levitt <jay+news@jay.fm> wrote:
> I had to write a script this evening to take an unsorted input file of the
> form:
>
> database 1 is on server 3
> database 8 is on server 7
> ...
>
> and output it in the form:
>
> server 3 handles database 1 through 7
> server 7 handles database 8 through 11
>
> I feel like there's a much nicer way to express this in Ruby, but can't
> think of what it might be...

Does this feel nicer?

$ cat db_ranges.rb && ruby db_ranges.rb
# db_ranges.rb
# 26 September 2007
#

require 'enumerator'

file =<<END
database 8 is on server 7
database 10 is on server 7
database 9 is on server 7
database 5 is on server 9
database 1 is on server 3
database 2 is on server 3
database 133 is on server 3
database 4 is on server 144
END


dbs = Hash.new {|h,k| h[k] = []}

file.each do |line|
 m = line.match(/^database (.*) is on server (.*)/)
 db_n = m[1].to_i
 server_n = m[2].to_i
 dbs[server_n] << db_n
end

dbs.each do |server, db|
  result = [[db[0]]]
  db.sort.each_cons(2) {|x, y| if y == x + 1 then result.last << y;
else result << [y]; end}
  result.each {|x| puts "Server #{server} handles databases #{x.first}
to #{x.last}"}
end

Server 144 handles databases 4 to 4
Server 7 handles databases 8 to 10
Server 3 handles databases 1 to 2
Server 3 handles databases 133 to 133
Server 9 handles databases 5 to 5

Kind regards,

Jesus.