A simple dragon curve algorithm

dragon_curve.rb

# Dragon Curve algorithm
# source: http://en.wikipedia.org/wiki/Dragon_curve
# Use: ruby dragon_curve.rb [number of iterations]

str = "R"

ARGV[0].to_i.times do 
  nstr = str.reverse
  
  for i in 0..nstr.length
    if nstr[i] == 82
      nstr[i] = "L"
    elsif nstr[i] == 76
      nstr[i] = "R"
    end
  end
  
  str = str + "R" + nstr
end

puts str