From: Bryan Weatherly <bryan.weatherly.ruby@...>
Date: 2007-05-20T23:37:08+09:00
Subject: Re: [QUIZ] Magic Squares (#124)

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Here is my solution.  I also used the steps from Wikipedia:

# magic_squares.rb
# Ruby Quiz (#124)

class MagicSquare

  def initialize(n)
    raise ArgumentError, "N must be an odd number." if n%2 == 0
    @n = n
    @square = fill
  end

  def fill
    square = Array.new(@n)
    square.each_index { |row| square[row] = Array.new(@n) }
    current = 1
    row = 0
    col = (@n/2+1)-1
    square[row][col] = current
    until current == @n**2
      current+=1
      row = move_down(row)
      col = move_down(col)
      unless square[row][col].nil?
        2.times { |i| row = move_up(row) }
        col = move_up(col)
      end
      square[row][col] = current
    end
    square
  end

  def move_down(val)
    if (val-1) > -1
      val -= 1
    else
      val = (@n-1)
    end
    val
  end

  def move_up(val)
    if (val+1) > (@n-1)
      val = 0
    else
      val += 1
    end
    val
  end

  def display
    header = "+" + "-" * (@n*5-1) + "+"
    puts header
    @square.each do |row|
      current = "| "
      row.each do |col|
        current << " " * ((@n**2).to_s.length - col.to_s.length)
        current << col.to_s + " | "
      end
      puts current
      puts header
    end
  end

end

if __FILE__ == $0
  square = MagicSquare.new(ARGV[0].to_i)
  square.display
end

----------------------
~/desktop $ ruby magic_squares.rb 9
+--------------------------------------------+
| 45 | 34 | 23 | 12 |  1 | 80 | 69 | 58 | 47 |
+--------------------------------------------+
| 46 | 44 | 33 | 22 | 11 |  9 | 79 | 68 | 57 |
+--------------------------------------------+
| 56 | 54 | 43 | 32 | 21 | 10 |  8 | 78 | 67 |
+--------------------------------------------+
| 66 | 55 | 53 | 42 | 31 | 20 | 18 |  7 | 77 |
+--------------------------------------------+
| 76 | 65 | 63 | 52 | 41 | 30 | 19 | 17 |  6 |
+--------------------------------------------+
|  5 | 75 | 64 | 62 | 51 | 40 | 29 | 27 | 16 |
+--------------------------------------------+
| 15 |  4 | 74 | 72 | 61 | 50 | 39 | 28 | 26 |
+--------------------------------------------+
| 25 | 14 |  3 | 73 | 71 | 60 | 49 | 38 | 36 |
+--------------------------------------------+
| 35 | 24 | 13 |  2 | 81 | 70 | 59 | 48 | 37 |
+--------------------------------------------+

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