gistfile1.rb

def make_square(n)
  height = Math.sqrt(n)
  throw "Input incorrect" unless height == height.to_i
  x = ((height - 1) / 2).floor
  y = ((height - 1) / 2).ceil
  height = height.to_i
  direction = 0
  mat = []
  (0 .. n - 1).each do |i|
    mat[y] ||= []
    mat[y][x] = i + 1
    case direction
      when 0 then x += 1; direction = 1 if x == height-1 || mat[y - 1].nil? || mat[y - 1][x].nil?
      when 1 then y -= 1; direction = 2 if y == 0 || mat[y].nil? || mat[y][x - 1].nil?
      when 2 then x -= 1; direction = 3 if x == 0 || mat[y + 1].nil? || mat[y + 1][x].nil?
      when 3 then y += 1; direction = 0 if y == height - 1 || mat[y].nil? || mat[y][x + 1].nil?
    end
  end

  print_square(mat)
end

def print_square(mat)
  offset = mat.flatten.max.to_s.size + 1
  res = mat.map do |coll|
    coll.map {|v| "%#{offset}d" % v.to_i }.join(' ')
  end.join("\n")

  puts res
end
 
make_square(5 ** 2)