Euler observed that the only relevant information here are the land masses (the nodes) and the connections between them (the bridges, or edges), which reduces the problem to a simple graph.

A graph G (V,E) is a finite, nonempty set of vertices, V, or nodes and a set of edges, E. If the edges E that have the form of (a,b) are ordered pairs of vertices, then we have a directed graph. If ...

In directed graphs, relationships are asymmetric and these asymmetries contain essential structural information about the graph. Directed relationships lead to a new type of clustering that is not ...