Graphs are useful for representing real-world data. Many practical problems can be represented by graphs. Therefore, they are becoming increasingly significant as they are applied to other areas of mathematics, science, and technology.
Your first association with the usage of graph theory is most probably social networks—sets of people or groups of people with some pattern of contact or interactions between them, such as Facebook, Twitter, Instagram, LinkedIn, and so on. Here are small graphs illustrating a few users of the first two social networks:
A simple weighted graph
The graph on the left side is undirected ...
