title: Big-O notation for two simple recursive functions
body: <p>I have two recursive functions in Python and simply just want to know the Big O Notation for them.  What is the Big O for each these?</p>
  
  <pre><code>def cost(n):
      if n == 0:
          return 1
      else:
          return cost(n-1) + cost(n-1)
  
  def cost(n):
      if n == 0:
          return 1
      else:
          return 2*cost(n-1)
  </code></pre>