title: Complexity of Heapsort algorithm
body: <p>In the book is written:</p>
  
  <blockquote>
    <p>The worst-case running time of heapsort is (nlgn). This is clear since
    sorting has a lower bound of (nlgn)</p>
  </blockquote>
  
  <p>But can someone help me and show me explicitly that the lower-bound of this function is equal to Omega(nlgn)?</p>