Definition of a graph
A graph \(G = (V, A)\) is a mathematical structure defined by the sets:
- \(V\), a finite and non-empty set of vertices, with \(|V| = n\);
- \(A\), a set of \(|A| = m\) edges, where each edge is an unordered pair of elements of \(V\).
In a simple undirected graph, we have \(A \subseteq \{\{u,v\} \mid u,v \in V,\; u \neq v\}\).