From: Ben Ford <fordbc@...>
Date: 2007-01-15T00:50:06+09:00
Subject: Re: Number Spiral (#109)

Here is my solution. I used a recursive printing routine to handle the
insides of the middle rows.

Ben

class NumberSpiral
  def initialize(n)
    @size = n
    @format = "%#{(n*n - 1).to_s.length+1}d"
    if n % 2 == 0
      @top_row = proc{|x| (x*(x-1)).upto(x*x-1) {|i| print_num(i) } }
      @bottom_row = proc{|x| ((x-1)*(x-1)).downto((x-1)*(x-2)) {|i|
print_num(i) } }
      @middle_first = proc{|x,row| print_num(x*(x-1)-row) }
      @middle_last = proc{|x,row| print_num((x-2)*(x-2)-1+row) }
    else
      @top_row = proc{|x| ((x-1)*(x-2)).upto((x-1)*(x-1)) {|i|
print_num(i) } }
      @bottom_row = proc{|x| (x*x-1).downto(x*(x-1)) {|i| print_num(i)
} }
      @middle_first = proc{|x,row| print_num((x-1)*(x-2)-row) }
      @middle_last = proc{|x,row| print_num((x-1)*(x-1)+row) }
    end
  end

  def print_num(i)
    printf @format, i
  end

  def print_row(size, row)
    if row == 0
      @top_row.call(size)
    elsif row == size - 1
      @bottom_row.call(size)
    else
      @middle_first.call(size, row)
      print_row(size-2, row-1)
      @middle_last.call(size, row)
    end
  end

  def print_clockwise
    @size.times {|i| print_row(@size, i) ; puts ; puts if i < @size-1 }
  end
end

if ARGV.size == 0 or not ARGV[0] =~ /^\d+$/
  puts "Usage:  #$0 N"
  puts "Output:  Prints a \"spiral\" of numbers that fill a NxN
square."
else
  NumberSpiral.new(ARGV[0].to_i).print_clockwise
end


On Jan 12, 9:29 am, Ruby Quiz <j...@grayproductions.net> wrote:
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> on Ruby Talk follow the discussion.  Please reply to the original quiz message,
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>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
> by Bob Showalter
>
> (Taken from the puzzle by William Wu athttp://www.ocf.berkeley.edu/~wwu/riddles/cs.shtml)
>
> [Editor's Note:  This was also a code golf problem a few months back:http://codegolf.com/oblongular-number-spirals --JEG2]
>
> Write a Ruby program to print out a "spiral" of numbers that fill a NxN square.
> Your program will take a single argument to specify the dimensions of the square
> (1 or higher). The number zero represents the center of the spiral, and the
> succeeding integers spiral out in a clockwise (or counterclockwise; your choice)
> direction from the center until the square is filled.
>
> Your program should write the output line by line, without using an array to
> build up the data first.
>
> Here's the output for an 8x8 spiral:
>
>         56   57   58   59   60   61   62   63
>
>         55   30   31   32   33   34   35   36
>
>         54   29   12   13   14   15   16   37
>
>         53   28   11    2    3    4   17   38
>
>         52   27   10    1    0    5   18   39
>
>         51   26    9    8    7    6   19   40
>
>         50   25   24   23   22   21   20   41
> 
>         49   48   47   46   45   44   43   42