title: Get the largest key in a dictionary
body: <p>I have a dictionary with keys that are ints. I would like to get the largest key. I don't keep track of keys so they might be consecutive (e.g. 1,2,3,4,5,6) but might skip (1,3,4,5) although I doubt that makes any difference.</p>
  
  <p>Do I just use a binary search or is there a method? As far as I see you can hardly beat binary search for such a simple task - maybe you can halve it.</p>