Tip:
Highlight text to annotate it
X
Hi everybody. Welcome back.
We're now starting Unit 2, which is going to focus on graphs and their growth.
Last time what we talked about was an introduction to the idea of an algorithm
and how different algorithms can let you do different things fast or slow
and starting talking a little bit about analyzing the running time of algorithms.
Now, for reasons that are not entirely clear to me,
even though this is a course about analyzing social networks,
a vast majority of our discussion last times was on multiplying numbers together.
There is a reason for that. It was a simple problem that is easy for everybody
to understand and appreciate where the algorithm choice can make a very, very big difference
in the behavior of the algorithm once it's implemented.
This time, we're going to focus on tools for analyzing growth rates
so that we have a way of counting up how long running time is going to be
that we can analyse more easily than actually counting in detail what every statement
is going to be.
At the same time, we're going to develop a feel for the kinds of graph networks
that are really important in analyzing social networks.
But, before we begin, we're going to try another little magic trick.
Here's a block of number that I mostly randomly generated--
a bunch of three-digit numbers--and I want you to figure out as quickly as you can
whether the product of all these numbers is divisible by 5
or if it's not divisible by 5.