title: Big-O complexity for n + n-1 + n-2 + n-3 + (...) + 1
body: <p>I was wondering.. what is the complexity of an algorithm that starts with n elements (which I run through doing whatever). I take one element off, I do it again.. I take off another element and do it again until I have just one element left.
  is it O(n log n)? I can't visualize it...</p>