Can adjacency lists be used in directed graphs? I've been reading: https://en.wikipedia.org/wiki/Adjacency_list



It says that that graph can be constructed with the list $\{b, c\}, \{a, c\}, \{a, b\}$.

However, what if I wanted to construct a directional list? Does $\{b, c\}$ point to $b$ or $c$?

How can you use a list to represent a directional graph?
Your graph is actually undirected. The notation is a list of edges in the graph. Since edges are undirected, each edge is a set of two vertices. Your lists contains three edges, since a triangle has three edges. It actually contains all possible edges involving the vertices $a,b,c$.

A directed graph is one in which edges consist of two ordered vertices. The edge points from the first vertex to the second. You can represent such a graph using a list of pairs.

Adjacency lists are a different data structure, which is described in the Wikipedia page you link to, so I skip its description here. It can be used for both undirected and directed graphs, in the natural way.