title: Probability of RANDOMIZED-QUICKSORT exceed worst case
body: <p>The question is from clrs (exercise 12.4-5)</p>
  
  <blockquote>
    <p><strong>Consider RANDOMIZED-QUICKSORT operating on a sequence of n input numbers.
    Prove that for any constant k > 0, all but O(1/n^k) of the n! input permutations 
    yield an O(n lg n) running time.</strong></p>
  </blockquote>
  
  <p>How can I build the model of worst case, and get the max bound of it.</p>