fibonacci.rb

def recursive_fib(n)
  n <= 1 ? n : recursive_fib(n - 1) + recursive_fib(n - 2)
end

# recursive_fib
# the method takes argument n (digit desired of fibonacci sequence)
# first checks if n equals either base case (0 and 1), if so, returns n
# if not, sum the two previous digits of n; this will result in two recursive actions, of which
# will continue until each recursion (and their subsequent recursions) reaches the base cases (0 and 1)
# and returns the [total] sum (the nth digit of the sequence)

def iterative_fib(n)
  fib_seq = []
  (0..n).each do |num|
    if num <= 1
      fib_seq << num
      # p "less than one seq = #{fib_seq}"
    else
      # p "n = #{n} // seq(-1) = #{fib_seq[-1]} // seq(-2) = #{fib_seq[-2]} // seq = #{fib_seq}"
      fib_seq << fib_seq[-1] + fib_seq[-2]
      # p "last is prev two added = #{fib_seq}"
    end
  end
  fib_seq.last
end

# iterative_fib
# the method takes argument n (digit desired of fibonacci sequence)
# from the first digit in the fibonacci sequence, 0, to n (digit desired),
# if n is either 0 or 1 append the number to the array [and return the last number in the array];
# otherwise, append the sum of the last two digits in the array (in this case, getting the first two digits from the right)
# to get the nth digit of the sequence [and return it]

# note: (0..n), the ".." infers that n is inclusive in the range

p recursive_fib(9)    #34
p iterative_fib(9)    #34

require 'benchmark'
num = 35
Benchmark.bm do |x|
  x.report("recursive_fib") { recursive_fib(num) }
  x.report("iterative_fib")  { iterative_fib(num)  }
end