>about graph theory, it's something that is rarely used, if I need to do something I can grab a book and check it, it's strange to remember this stuff when you

>about graph theory, it's something that is rarely used, if I need to do something I can grab a book and check it, it's strange to remember this stuff when you don't use it a lot. I don't think you appreciate how pervasively useful a basic understanding of graph theory can be. For example, Google was founded around the idea of viewing the internet as a graph of hyperlinks (and decomposing its adjacency matrix to rank sites relative to each other). All that wacky data on the internet is easier to deal with if you can think about its graph structure. Social network? Graph. Language model? Graph. Road network? Graph. etc... This is a tool for thinking, not some particular API you can look up in a reference. You should be able to reason about the sparsity of the graph (and hence what sort of adjacency representation to use), the degree of the vertices (and thus how badly a search algorithm might perform), etc...