In mathematics, a graph is an abstract set of points (vertices) and lines (edges) that connect the vertices. A graph is an abstraction widely used to symbolically represent such varying things as electrical circuitry, computer networks, molecular diagrams, transportation and traffic problems, pipeline flows, and so on. The theory of graphs is intimately connected with topology, combinatorics, electrical engineering, computer science, and many other fields and disciplines. Graphs have been used to model social structures (think about a family tree, which is just a special kind of graph representing ancestor-descendant relationships) and other problems in the humanities where relationships between multiple entities needs to be symbolically represented. The study and design of graph algorithms is a primal concern in computer science.

Graph theory had its origins in a seminal 1736 contribution of the famous Swiss mathematician Leonhard Euler, who was then living in Germany. In Königsberg, Germany...