title: What is O(log(n!)), O(n!), and Stirling's approximation?
body: <p>What is <code>O(log(n!))</code> and <code>O(n!)</code>? I believe it is <code>O(n log(n))</code> and <code>O(n^n)</code>? Why?</p>
  <p>I think it has to do with <a href="https://en.wikipedia.org/wiki/Stirling%27s_approximation" rel="nofollow noreferrer">Stirling's approximation</a>, but I don't get the explanation very well.</p>
  <p>Am I wrong about <code>O(log(n!)</code> = <code>O(n log(n))</code>? How can the math be explained in simpler terms? In reality I just want an idea of how this works.</p>