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Zebra Graph


ZebrasTour

A zebra graph is a graph formed by all possible moves of a hypothetical chess piece called a "zebra" which moves analogously to a knight except that it is restricted to moves that change by two squares along one axis of the board and three squares along the other. To form the graph, each chessboard square is considered a vertex, and vertices connected by allowable zebra moves are joined by edges. The graphs above give the positions on square chessboards that are reachable by zebra moves. Zebra graphs are therefore (2,3)-leaper graphs, as well as Euclidean distance graphs with distance sqrt(13).

Zebra graphs are bicolorable, bipartite, class 1, perfect, triangle-free, and weakly perfect.

The square (n×n) zebra graph is connected for n=1 and n>=6.

For n×n square boards, the zebra graph is traceable exactly when n=1, n=10, or n>=14. This can be proved as follows. For board sides 14 through 23, construct Hamiltonian paths with two chosen corner edges. Add strips of width 10 on the right and along the bottom, and join the strips' Hamiltonian cycles to the original Hamiltonian path. This gives a Hamiltonian path on a board of side n+10 with the corner edges needed to repeat the construction (E. Weisstein, Oct. 5, 2026).

The smallest nontrivial square board where a Hamiltonian cycle exists (i.e., for which the underlying zebra graph is Hamiltonian) is the 10×10 board, first solved by Frost (1886, cited by Jelliss 2019). There are a total of 80320 Hamiltonian cycles on this board. For n<=20, the square board is Hamiltonian for exactly n=1, 10, 14, 16, 18, and 20. The square zebra graph is also Hamiltonian for all sufficiently large even n (Beluhov 2022).

Precomputed properties of zebra graphs are implemented in the Wolfram Language as GraphData[{"Zebra", {m, n}}].


See also

Antelope Graph, Camel Graph, Fairy Chess, Fiveleaper Graph, Giraffe Graph, Knight Graph, Leaper Graph

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References

Beluhov, N. "Leaper Tours." Advances in Combinatorics 2022, Article 4, 1-32, 2022. https://doi.org/10.19086/aic.2022.4.Cross, H. H. Problem 4709 in Fairy Chess Review. Feb. 1941.Frost, A. H. Plate VII in M. Frolow. Les Carrés Magiques. Paris, France, 1886.House of Graphs. Zebra Graphs. 6x6 (2,3)-leaper Graph, 10x10 (2,3)-leaper Graph, 13x13 (2,3)-leaper Graph, and others.Jelliss, G. "The Big Beasts: Zebra {2, 3}." §10.31 in Knight's Tour Notes. 2019. https://www.mayhematics.com/ktn/KTN10_Leapers.pdf.Jelliss, G. Chessics.Jelliss, G. P. "Generalized Knights and Hamiltonian Tours." J. Recr. Math. 27, 191-200, 1995.Jelliss, G. P. "Longer Leaper Tours with Quaternary Symmetry." The Games and Puzzles Journal 2, No. 2, p. 290, 1999.Kraitchik, M. Mathematical Recreations. New York: W. W. Norton, pp. 70-73, 1942.Willcocks, T. H. Chessics. 1978.

Referenced on Wolfram|Alpha

Zebra Graph

Cite this as:

Weisstein, Eric W. "Zebra Graph." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ZebraGraph.html

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