fibonacci.rb

def fibonacci_iterative(n)
  return 0 if n==0
  return 1 if n==1

  second_previous_num=0
  first_previous_num=1

  until n == 1
  	sum_of_two_num= first_previous_num + second_previous_num  #if n==2, sum_of_two_num=1  
  	second_previous_num=first_previous_num #if n==2, second_previous_num=1   
  	first_previous_num=sum_of_two_num #if n==2, first_previous_num=1 
  	n-=1
  end
  sum_of_two_num # return 1
end

def fibonacci_recursive(n)
  return 0 if n==0
  return 1 if n==1
  
    fibonacci_recursive(n - 1) + fibonacci_recursive(n - 2) # recursion is called
  
end
 
puts fibonacci_recursive(0) == 0  # straight return 0  
puts fibonacci_recursive(1) == 1  # straight return 1
puts fibonacci_recursive(2) == 1  # start evaluating by calling its method again until u get the value
puts fibonacci_recursive(3) == 2
puts fibonacci_recursive(4) == 3
puts fibonacci_recursive(5) == 5
puts fibonacci_recursive(6) == 8
puts fibonacci_recursive(7) == 13