title: change element equal to pivot in quicksort
body: <p><strong>why is it benefic for the quicksort to change (in partition void) elements that has the same value as the pivot?</strong></p>
  
  <p>I was asked that but I don't know why... maybe cos if they dont change, the array may stay unordered?</p>
  
  <pre><code>1 3 5 [3] 2 6
      i     j     swap to
  
  1 3 2 [3] 5 6
  </code></pre>
  
  <p>and it will make any more swaps later for some reason? I dont know...</p>
  
  <p>I'd like to know why swapping the elements with same value as the pivot is a good thing.</p>