From: James Edward Gray II <james@...>
Date: 2006-08-28T09:03:46+09:00
Subject: Fwd: Please Forward: Ruby Quiz Submission

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Begin forwarded message:

> From: Ken Bloom <kbloom@gmail.com>
> Date: August 27, 2006 12:51:01 PM CDT
> To: submission@rubyquiz.com
> Subject: Please Forward: Ruby Quiz Submission
>
> This is a recursive solution that runs in linear time (well, after
> sorting).
>
> --Ken Bloom
>
> -- 
> Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
> Department of Computer Science. Illinois Institute of Technology.
> http://www.iit.edu/~kbloom1/
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NAMEMAP={"Mon"=>1,"Tue"=>2,"Wed"=>3,"Thu"=>4,"Fri"=>5,"Sat"=>6,"Sun"=>7,"Thurs"=>4,
"Monday"=>1,"Tuesday"=>2,"Wednesday"=>3,"Thursday"=>4,
"Friday"=>5,"Saturday"=>6,"Sunday"=>7}

REVERSENAMEMAP=[nil,"Mon","Tue","Wed","Thu","Fri","Sat","Sun"]

}


def dayrange(*args)
   args.collect!{|x| NAMEMAP[x] || x}
   raise ArgumentError if args.any?{|x| not x.is_a?(Fixnum) or not (1..7).include?(x)}

   class << args
      def combine!(idx)
	 return if idx>=length-1
	 if x=combineelements(self[idx],self[idx+1])
	    self[idx]=x
	    self.delete_at(idx+1)
	    combine! idx
	 end
      end
      def combineelements(elem1,elem2)
	 if elem1.is_a?(Range) and elem1.last+1==elem2
	    ((elem1.first)..elem2) 
	 elsif elem1.is_a?(Numeric) and elem1+1==elem2
	    (elem1..elem2)
	 else
	    nil
	 end
      end
   end

   args.sort!.uniq!
   x=0
   while x < args.length
      args.combine!(x)
      x+=1
   end

   args.collect do |x|
      if x.is_a? Range and x.first+1==x.last
	 [REVERSENAMEMAP[x.first],REVERSENAMEMAP[x.last]]
      elsif x.is_a? Range
	 REVERSENAMEMAP[x.first]+"-"+REVERSENAMEMAP[x.last]
      else
	 REVERSENAMEMAP[x]
      end
   end.flatten.join(",")
end

dayrange(1,2,3,5,7)

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