What is a graph data structure and how is it used in real-world applications?

A graph is a data structure consisting of a set of vertices (also known as nodes or points) and a set of edges (also known as links or lines) connecting them. Graphs can be used to represent a wide range of real-world systems and relationships, including social networks, transportation networks, computer networks, and more. In a graph, vertices represent entities, such as people, cities, or computers, and edges represent relationships between them, such as friendships, roads, or network connections. Each edge can have a weight or cost associated with it, representing the strength or distance of the relationship between the vertices. There are two common types of graphs: directed graphs (also known as digraphs) and undirected graphs. In a directed graph, the edges have a direction and indicate a one-way relationship between vertices. In an undirected graph, the edges do not have a direction and represent a two-way relationship be....