title: Find the 10 most frequently used words in a large book
body: <p>I am aware that this has been asked on the forum a couple of times, I did not find any 'TAGGED' answer which could be considered the most appropriate soluion - so asking again:</p>
  
  <p>We are given a very large text from book all of which cannot fit into the memory. We are required to find the top 10 most frequently occuring words in the text. What would be the most optimal (time and space) way to do this?</p>
  
  <p>My thought:</p>
  
  <p>Divide the file into k-sizeable chunks (such that each of the chunks can be stored in the memory). Now, perform an external sort on each of the chunks. Once we have the (N/k)- sorted files on the disk (assuming N is the total size of the text from the book) - I am not sure how should I continue so that I can obtain the top 10-elements from the k-sorted arrays.</p>
  
  <p>Also, if there is a different line of thought, please suggest.</p>