Teaching mathematics bass-ackwards
I have now taught the " master method " for solving recurrences twice. The first time I managed to muddle through and present the gist of the idea without screwing up too much. But when I revisited it this semester, I was able to develop a pretty complete intuition for why it works and what is going on. And to realize that one of the world's leading algorithm books presents this in a completely backwards fashion. The student is presented with page after page of formalism, and left to work out what the hell is going on on their own. To present it properly, show how historically the theorem developed out of solving recurrences with recursion trees. Solve a few from each type of case (three) the master method contains. Lead the students to see that the trees keep falling into one of these three categories. Show how which category they fall into depends on the values of a, b, and x in the equation: T(n) = aT(n / b) + n x Then suggest, "Hey, perhaps we can state ...