```Begin forwarded message:

> From: "Mark Harris" <mdh103 / soton.ac.uk>
> Date: January 16, 2007 2:06:47 PM CST
> To: submission / rubyquiz.com
> Subject: Please Forward: Ruby Quiz Submission
>
> Hi
>
> My first submission, not been using Ruby that long and come from a
> couple of years learning Java at Uni, which probably shows.
> Thanks for running and hosting the quizzes, trawling through the
> archive was very informative.
>
> Mark Harris
>
> class NumberSpiral
>
> include Enumerable
>
> def initialize(dimension)
> @n = dimension
> @even = dimension % 2
> @maxSize = (@n**2 - 1).to_s.length
> end
>
> def each
> @line=0
> (0..@n-1).map { yield nextLine }
> @line=0
> end
>
> private
>
> def nextLine
> result = spiral(@n, @line)
> @line+=1
> result.map{ |x| x.to_s.center(@maxSize) }.join(" ")
> end
>
> def spiral(n, l)
> if (n==1)
> 0
> elsif (n % 2 ==0)
> #Even
> if (l == 0)
> # Top row, just return it.
> (n**2 - n)..(n**2-1)
> else
> # Same as the square of size (n-1) at line (l-1) with this square's
> number in front.
> ([(n**2 - n - l)] << spiral(n-1,l-1)).flatten
> end
> else
> #Odd
> if (l==(n-1))
> # Bottom row, just return it
> a = Array.new
> (n**2-1).downto(n**2-n) { |x| a << x}
> a
> else
> #Same as the square of size (n-1) at line l with this square's
> number at the end.
> (spiral(n-1,l).to_a << [(n ** 2 - 2*n + 1 + l)]).flatten
> end
> end
> end
> end
>
> spiral = NumberSpiral.new((ARGV || 9).to_i)
> spiral.each {|x| puts x }

```