title: What is the quickest way to find all missing numbers in unsorted array
body: <p>I found this answer: <a href="https://stackoverflow.com/questions/2113795/quickest-way-to-find-missing-number-in-an-array-of-numbers">Quickest way to find missing number in an array of numbers</a>, which is great when you have only one number missing.</p>
  
  <p>Further to that question - I have wondered what is the best (and quickest) way of finding all missing numbers and also to sort the unsorted array. (for the example the array is like the one was described in the linked question - the array size is 100, with random numbers from 1-100, but some of them are missing)</p>