title: Does Insertion Sort always take N-1 comparasons on a sorted list?
body: <p>I just finished the old "Sorting Detective" homework (where you are given a few black box sorting algorithms and have to determine what example each one is by the results), and I noticed that Insertion Sort always took N-1 comparisons on a sorted list. Since I won't be able to look at my instructor's code until everyone has turned in their assignments, nor am I allowed to ask questions in class that could tip off the other students as to how to proceed to solve the problem, this left me with a question I can't get the answer to this question for at least a week. </p>
  
  <p>Is it always the case in the real world that a textbook example of Insertion Sort will do N-1 comparisons on a sorted list, or is it quirk of my instructor's/textbook's version of Insertion Sort?</p>
  
  <p>After searching Google and the Wikipedia, I couldn't find the answer to this, which means either I'm asking the wrong question or they just don't have it. Any ideas?</p>