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arXiv 1402.0545math.CO
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方格图上非同构哈密顿圈的Enumeration

Enumeration of nonisomorphic Hamiltonian cycles on square grid graphs

Ed Wynn

摘要:

2n × 2n网格上哈密顿圈的计数是组合数学中一个长期存在的问题。以前的工作集中在计算所有周期。目前的工作列举了非同构循环-也就是同构类的数量(直到正方形的所有对称运算)。它示出,以前使用的矩阵方法可以修改为计数周期与反射和180度旋转对称的所有组合。90度旋转对称的周期通过直接搜索来计数,使用Knuth的Dancing Links算法的修改。从这些计数中,计算出n<=10时的非同构圈数。

英文摘要:

The enumeration of Hamiltonian cycles on 2n*2n grids of nodes is a longstanding problem in combinatorics. Previous work has concentrated on counting all cycles. The current work enumerates nonisomorphic cycles -- that is, the number of isomorphism classes (up to all symmetry operations of the square). It is shown that the matrix method used previously can be modified to count cycles with all combinations of reflective and 180-degree rotational symmetry. Cycles with 90-degree rotational symmetry were counted by a direct search, using a modification of Knuth's Dancing Links algorithm. From these counts, the numbers of nonisomorphic cycles were calculated for n<=10.

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