Fig. 3

Graph representation. All graph representations refer to the same undirected graph (Graph G) in the top left corner but are presented in three different formats. a Adjacency matrix of graph G. Each element of the graph has a value of one is there exists an edge between the node listed in the beginning of the row and the node listed at the top of the column. Note that this matrix is symmetrical as undirected graphs have no directionality to their edges. b Adjacency list of graph G. Each entry in the list correspond to a unique node in the graph. A link (represented here by arrows) is then provided to each node to has an edge with the corresponding node. The list of interacting nodes is represented by empty squares pointing to the vertex id. The end of the list of nodes is represented by a square with a cross. c Canonical code of graph G with adjacency matrix A(G). This is a string concatenation of the upper triangle of the adjacency matrix representation