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arXiv 1111.0406math.COcs.DM
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图的图不变量与2-因子分解

A Graph Invariant and 2-factorizations of a graph

Yingtai Xie

摘要:

图G的一个生成子图称为G的一个[0,2]-因子,如果图G是由若干个不相交的圈、路和孤立点组成的并。G的一个[0,2]-因子很容易求出,而一个G的[0,2]-因子会有很多个.定义了一个[0,2]-因子的示性数,它反映了其中的路数和孤立点数.如果图G的示性数最小,则称图G的[0,2]-因子最大,称为图G的示性数.本文证明了图的示性数是图不变量,并给出了求图G的最大[0,2]-因子的多项式时间算法. [0,2]-因子称为2-因子,如果它的示性数为零。我们提出了一个由[0,2]-因子计算2-因子的A多项式时间算法,该算法易于实现。一个哈密尔顿圈是一个2-因子,因此哈密尔顿图的一个必要条件是图有2-因子或图的示性数为零。本文给出的算法使在多项式时间内检验该条件成为可能。

英文摘要:

A spanning subgraph of a graph G is called a [0,2]-factor of G, if for . is a union of some disjoint cycles, paths and isolate vertices, that span the graph G. It is easy to get a [0,2]-factor of G and there would be many of [0,2]-factors for a G.A characteristic number for a [0,2]-factor, which reflect the number of the paths and isolate vertices in it,is defineted. The [0,2]-factor of G is called maximum if its characteristic number is minimum, and is called characteristic number of G.It to be proved that characteristic number of graph is a graph invariant and a polynomial time algorithm for computing a maximum [0,2]-factor of a graph G has been given in this paper. A [0,2]-factor is Called a 2-factor, if its characteristic number is zero. That is, a 2-factor is a set of some disjoint cycles, that span G.We propose a A polynomial time algorism for computing 2-factor from a [0,2]-factor,which can be got easily. A HAMILTON Cycle is a 2-factor, therefore a necessary condition of a HAMILTON Graph is that, the graph have a 2-factor or the characteristic number of the graph is zero. The algorism, given in this paper, make it possible to examine the condition in polynomial time.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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