Collatz.rb

=begin

A collatz sequence, starting with a positive integern, is found by repeatedly
applying the following function to n until n == 1 :

collatz sequence

 n = { n / 2 for even n ;
      3n + 1 for odd n }

A more detailed description of the collatz conjecture may be found on Wikipedia.

The Problem

Create a function collatz that returns a collatz sequence string starting with
the positive integer argument passed into the function, in the following form:

"X0->X1->...->XN"

Where Xi is each iteration of the sequence and N is the length of the sequence.

Sample Input

collatz(4) # should return "4->2->1"
collatz(3) # should return "3->10->5->16->8->4->2->1"

=end

# My Solution
def collatz(n)
  return "1" if n==1
  result = ["#{n}"]
  begin
    n % 2 != 0 ? n = n * 3 + 1 : n = n / 2
    result << ["#{n}"]
  end while n != 1
  result.join("->")
end

# Better Solution
def collatz(n)
  n>1? n.to_s+'->'+collatz( n%2==1? n*3+1 : n/2 ):'1'
end