Bond graph creation

Figure 2 shows an example for the enumeration of chemical graphs by using the connectivity stack method. Nodes W, X, Y, Z in this figure have atomic valences 2, 2, 1, 1, respectively, and the priority order of these nodes is assumed to be W > X > Y = Z. Furthermore, nodes Y and Z are equivalent in this example. The connectivity stack starts by creating a bond between W and X on a connectivity matrix (ai2 = 1, i.e., bi = 1). The principles for the creation of a connectivity stack are to start to create a bond from the head of a connectivity stack, to examine the valency of each node, and not to generate separated chemical graphs (examination of connectivity). 

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