Jun-qing CAI, Lin WANG
In 2005, Flandrin et al. proved that if G is a k-connected graph of order n and V(G)=X1 ∪ X2 ∪ … ∪ Xk such that d(x)+ d(y) ≥ n for each pair of nonadjacent vertices x, y ∈ Xi and each i with i=1, 2, …, k, then G is hamiltonian. In order to get more sufficient conditions for hamiltonicity of graphs, Zhu, Li and Deng proposed the definitions of two kinds of implicit degree of a vertex v, denoted by id1(v) and id2(v), respectively. In this paper, we are going to prove that if G is a k-connected graph of order n and V (G)=X1 ∪ X2 ∪ … ∪ Xk such that id2(x) + id2(y) ≥ n for each pair of nonadjacent vertices x, y ∈ Xi and each i with i=1, 2, …, k, then G is hamiltonian.