title: Generate list of unique random numbers in constant time
body: <p>I need 100 random numbers from the range 1 to 1,000,000. The numbers must be unique, no duplicates.
  It's similar to <a href="https://stackoverflow.com/questions/196017/unique-random-numbers-in-o1">this question</a>, but my range is too large to create an array from.</p>
  
  <p>I need to generate these 100 random numbers many, many times, so generation needs to be as fast as possible, preferably O(1). What's the fastest way to do it?</p>