collatz.rb

#generates a collatz sequence for input n
def generate_sequence(n)
    seq = [n]
    while (n != 1) do
      n.even? ? n /= 2 : n = (3 * n + 1)
      seq << n
    end
    return seq
end
#finds number with the longest collatz sequence between 1 and 1 million
def find_longest_sequence
  highest_length = 0
  number = 0
  i = 1
  while (i < 1000000) do
    new_length = generate_sequence(i).length
    if (new_length > highest_length)
      highest_length = new_length
      number = i
      i+=1
    else
      i+=1
    end
  end
  puts "The number with the longest collatz sequence is: #{number} with a length of #{highest_length}."
end

find_longest_sequence