Introducing graph properties
In graph theory, a graph is a mathematical structure consisting of a set of objects, called vertices or nodes, and a set of connections, called edges, which link pairs of vertices. The notation 
is used to represent a graph, where 
is the graph, 
is the set of vertices, and 
is the set of edges.
The nodes of a graph can represent any objects, such as cities, people, web pages, or molecules, and the edges represent the relationships or connections between them, such as physical roads, social relationships, hyperlinks, or chemical bonds.
This section provides an overview of fundamental graph properties that will be used extensively in later chapters.
Directed graphs
One of the most basic properties of a graph is whether it is directed or undirected. In a directed graph, also called a digraph, each edge has a direction or orientation. This means that the edge connects two nodes in a particular direction, where one node is the source and the other...
