title: multi-way merge vs 2-way merge
body: <p>When we <a href="http://en.wikipedia.org/wiki/External_sorting" rel="nofollow">externally merge sort</a> a large file, we split it into small ones, sort those, and then merge them back into a large sorted file.</p>
  
  <p>When merging, we can either do many 2-way merge passes, or one multi-way merge. </p>
  
  <p>I am wondering which approach is better? and why?</p>