Print a spiral matrix.

gistfile1.rb

def print_spiral(mat)
  layers = (mat.length.to_f / 2).ceil
  layers.times do |layer|
    print_layer(mat, layer, layers)
  end
end

def print_layer(mat, layer, layers)
  if mat.length.odd? and (layer == layers - 1)
    puts mat[layer][layer]
  else
    print_top(mat, layer)
    print_right(mat, layer)
    print_bottom(mat, layer)
    print_left(mat, layer)
  end
end

def print_top(mat, layer)
  row = layer
  layer.upto(mat.length-layer-2) do |col|
    puts mat[row][col]
  end
end

def print_right(mat, layer)
  col = mat.length-1-layer
  layer.upto(mat.length-layer-2) do |row|
    puts mat[row][col]
  end
end

def print_bottom(mat, layer)
  row = mat.length-1-layer
  (mat.length-1-layer).downto(layer+1) do |col|
    puts mat[row][col]
  end
end

def print_left(mat, layer)
  col = layer
  (mat.length-1-layer).downto(layer+1) do |row|
    puts mat[row][col]
  end
end

def init_matrix(size)
  (1..size**2).each_slice(size).to_a
end

print_spiral(init_matrix(4))