3n + 1

three_n_plus_one.rb

filename = ARGV

input = Array.new
output = Array.new

File.open(filename.first) do |f|
  while line = f.gets
    input << line.chomp!.split(" ")
  end
end

input.each do |x, y|
  max = 0
  output << x + ' '
  output << y + ' '
  x.to_i.upto(y.to_i) do |i|
    cycle = 1
    while i != 1
      if i.even?
        i = i / 2
      else
        i = i * 3 + 1
      end
      cycle += 1
    end
    max = cycle if cycle > max
  end 
  output << max.to_s + "\n"
end

puts output.join