The Cartesian product of two hamiltonian graphs is always hamiltonian. For directed graphs, the analogous statement is false. We show that the Cartesian product C,,, x C, , of directed cycles is hamiltonian if and only if the greatest common divisor (g.c.d.) d of n, and n, is a t least two and there
When the cartesian product of two directed cycles is hypo-Hamiltonian
β Scribed by Laurence E. Penn; David Witte
- Publisher
- John Wiley and Sons
- Year
- 1983
- Tongue
- English
- Weight
- 150 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
β¦ Synopsis
We show that the Cartesian product Z, x Z, of two directed cycles is hypo-Hamiltonian (Hamiltonian) if and only if there is a pair of relatively prime positive integers m and n with ma + nb = ab -1 (ma + nb = ab). The result for hypo-Hamiltonian is new; that for Hamiltonian is known. These are special cases of the fact that there is a simple circuit of length p in Z, x Z, if and only if there is a pair of relatively prime non-negative integers m and n with ma + nb = p < ab.
π SIMILAR VOLUMES
We say a digraph G is hyperhamiltonian if there is a spanning closed walk in G which passes through one vertex exactly twice and all others exactly once. We show the Cartesian product Z, x Z, of two directed cycles is hyperhamiltonian if and only if there are positive integers rn and n with ma + nb
We find necessary and sufficient conditions for the existence of a closed walk that traverses r vertices twice and the rest once in the Cayley digraph of 2, @ 2,. This is a generalization of the results known for r = 0 or 1. In 1978, Trotter and Erdos [3] gave a necessary and sufficient condition f
## Abstract We show that the Cartesian product of two directed cycles __Z__~__a__~ X __Z__~__b__~ has __r__ disjointly embedded circuits __C__~1~, __C__~2~, β, __C__~r~ with specified knot classes knot__(C~i~) = (m~i~, n~i~)__, for __i__ = 1, 2, β, __r__, if and only if there exist relatively prime