title: Remove duplicates from array in linear time and without extra arrays
body: <p>We have an array and it is unsorted. We know the range is [0,n].</p>
  
  <p>We want to remove duplicates but we <strong>cannot use extra arrays</strong> and it must <strong>run in linear time</strong>.</p>
  
  <p>Any ideas? Just to clarify, this is not for homework!</p>