顺时针从外到内打印数字矩阵

# 打印数字矩阵到标准输出。
# 按顺时针方向，从外到内打印矩阵。起点是矩阵的左上角。

class Matrix
	def initialize(width)
			@n = 0 
			@width = width  #矩阵的宽度

			# 创建二维数组
			@square = Array.new(@width) do
					Array.new(@width, 0)
			end
	end

	# 打印矩阵
	def print_matrix
			@square.each do |line|
					line.each do |n|
						printf("%-3d", n)
					end
					puts
			end
	end

	# 填充矩阵。
	# start 遍历的起点
	def fill_in_the_matrix(start)

		# 结束递归的条件
		return if start > (@width-1)/2
		
		#从左到右遍历
		start.upto(@width-start-1) do |i|
			@square[start][i] = @n += 1
		end		

		#从上到下遍历
		(start+1).upto(@width-start-1) do |i|
			@square[i][@width-start-1] = @n += 1
		end

		#从右到左遍历
		(@width-start-2).downto(start) do |i|
			 @square[@width-start-1][i] = @n += 1
		end

		#从下到上遍历
		(@width-start-2).downto(start+1) do |i|
			@square[i][start] = @n += 1
		end

		fill_in_the_matrix(start+1)
	end
end

m = Matrix.new(ARGV[0].to_i)
m.fill_in_the_matrix(0)
m.print_matrix