6 two graphs are isomorphic when the vertices of one can be re labeled to match the 5149489
6. Two graphs are isomorphic when the vertices of one can be re-labeled to match the vertices of the other in a way that preserves adjacency. More formally, a graph Gı is isomorphic to a graph G2 if there exists a one-to-one function f, called an isomorphism, from Vı (the vertex set of Gı) onto V2 such that (ui, vi) is an element of Ei (the edge set of Gı) if and only if (uz, v2) is an element of E2. GRAPH-ISO-