where the maximum is taken over all cyclic ordering s of V(G). therefore,H+(G) = 8 for the graph G of of figure 6.22.
As another example,we consider the Petersen graph.Label the vertices of the Petersen graph PG as shown in figure 6.23 .Since PG is a non-Hamiltonian graph of order 10,h(PG) ≥ 11.on the other hand,let be 1 .Hence