As far as I know, for two undirected graphs $G = (V, E) $ and $H = (V', E')$, the following criteria is necessary for them to be isomorphic:
- $|V| = |V'|$
- $|E| = |E'|$
- $G$ has $j$ nodes of degree $k$ $\Leftrightarrow $ $H$ has $j$ nodes of degree $k$
Are there more that are that obvious? Thanks in advance for your help!