turtle_tracks.rb

def fd(canvas, pos_x, pos_y, units, dir)
    units.times do
      pos_y = if dir == "N" || dir == "NE" || dir == "NW"
                pos_y - 1
              elsif dir == "S" || dir == "SE" || dir == "SW"
                pos_y + 1
              else
                pos_y
              end
      pos_x = if dir == "E" || dir == "NE" || dir == "SE"
                pos_x + 1
              elsif dir == "W" || dir == "NW" || dir == "SW"
                pos_x - 1
              else
                pos_x
              end

      canvas[pos_y][pos_x] = "X"
    end
    
    [pos_x, pos_y]
end

def bk(canvas, pos_x, pos_y, units, dir)
    units.times do
      pos_y = if dir == "N" || dir == "NE" || dir == "NW"
                pos_y + 1
              elsif dir == "S" || dir == "SE" || dir == "SW"
                pos_y - 1
              else
                pos_y
              end
      pos_x = if dir == "E" || dir == "NE" || dir == "SE"
                pos_x - 1
              elsif dir == "W" || dir == "NW" || dir == "SW"
                pos_x + 1
              else
                pos_x
              end

      canvas[pos_y][pos_x] = "X"
    end

    [pos_x, pos_y]
end

def rt(degrees, current_direction)
  transitions = { "N" => "NE", "NE" => "E", "E" => "SE", "SE" => "S", "S" => "SW", "SW" => "W", "W" => "NW", "NW" => "N" }

  if degrees < 0
    until degress >= 0 
      degress += 180
    end
  elsif degrees >= 180
    until degrees < 180 do
      degrees -= 180
    end
  end

  (degrees / 45).times do
    current_direction = transitions[current_direction]
  end

  current_direction
end

def lt(degrees, current_direction)
  rt(180 - degrees, current_direction)
end


size = gets.to_i
gets

canvas = []
size.times do
  row = []
  size.times do
    row << '.'
  end
  canvas << row
end

pos_x = (size - 1) / 2
pos_y = (size - 1) / 2
dir = "N"

canvas[pos_y][pos_x] = 'M'

until (instr = gets).nil?
  command = instr.split(" ").first

  if command == "FD" || command == "BK"
    units = instr.split(" ").last.to_i
    pos_x, pos_y = (command == "FD") ? fd(canvas, pos_x, pos_y, units, dir) : bk(canvas, pos_x, pos_y, units, dir)
  elsif command == "RT" || command == "LT"
    degrees = instr.split(" ").last.to_i
    dir = (command == "RT") ? rt(degrees, dir) : lt(degrees, dir)
  else
    elements = instr.split(" ")
    times = elements[1].to_i

    index = 3
    instructions = []
    until elements[index] == ']'
      instructions << [elements[index], elements[index + 1]]
      index += 2
    end

    times.times do
      instructions.each do |inst|
        if inst.first == "FD" || inst.first == "BK"
          units = inst.last.to_i
          pos_x, pos_y = (inst.first == "FD") ? fd(canvas, pos_x, pos_y, units, dir) : bk(canvas, pos_x, pos_y, units, dir)
        elsif inst.first == "RT" || inst.first == "LT"
          degrees = inst.last.to_i
          dir = (inst.first == "RT") ? rt(degrees, dir) : lt(degrees, dir)
        end
      end
    end
  end
end

canvas.each do |row|
  puts row.join(" ")
end