Graph Theory The edges in a directed graph are arrows pointing to one endpoint or the other. Here an exampl t Directed graphs are often called digraphs. We denote an edge from vertex A to vertex in a digraph by A- B. Formally, the edges in a directed graph ed are ordere Pairs of vertices rather than sets of two vertices. The number of edges directed into a vertex is called the in-degree of the vertex, and the number of edged directed out is called the out-degree One can also allow self-loops, edges with both endpoints at one vertex. He re is an example of a graph with self-loops Combinations of these variations are also possible for example, one could work with directed multigraphs with self-loops Except where stated otherwise, the word"graph" in this course refers to a graph without mul- tiple edges, directed edges, or self-loops4 Graph Theory The edges in a directed graph are arrows pointing to one endpoint or the other. Here is an example: Directed graphs are often called digraphs. We denote an edge from vertex A to vertex B in a digraph by A −→ B. Formally, the edges in a directed graph are ordered pairs of vertices rather than sets of two vertices. The number of edges directed into a vertex is called the in­degree of the vertex, and the number of edged directed out is called the out­degree. One can also allow self­loops, edges with both endpoints at one vertex. Here is an example of a graph with self­loops: Combinations of these variations are also possible; for example, one could work with directed multigraphs with self­loops. Except where stated otherwise, the word “graph” in this course refers to a graph without mul￾tiple edges, directed edges, or self­loops