Unit 5 combines ideas from graph search that we studied in Unit 3 with ideas about computing statistic that we look at in Unit 4 and it puts these tools together to give us the way of finding shortest path in these networks. Social networks come in many different flavors. Some of them consist of simple yes/no connections between the individuals in the network but others include more detailed information about the strength of those connections. We'll also going to look at approximation algorithms which are key tools for applying algorithms to a very large data seqs like these social networks. Let's get started.