arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1906.04062cs.DSmath.CO
收藏

求群标号图的最短非零路

Finding a Shortest Non-zero Path in Group-Labeled Graphs

Yoichi Iwata, Yutaro Yamaguchi

摘要:

研究了一类具有非负边长的群标号图的约束最短路问题,称之为最短非零路问题。根据所讨论的组,这个问题包括两种类型的易处理的变种无向图:一个是奇偶约束的最短路径/循环问题,另一个是计算表面嵌入图中的最短不可收缩循环。对于有限阿贝尔群的最短非零路径问题,Kobayashi和Toyooka(2017)通过永久计算提出了一种随机伪多项式时间算法。对于稍微更一般的一类群,Yamaguchi(2016)将问题简化为加权线性拟阵奇偶问题。特别是,一些情况下解决强多项式时间通过减少与一个确定性的,多项式时间算法的加权线性拟阵奇偶问题的帮助下,由岩田和小林(2021),这推广了一个众所周知的事实,奇偶约束的最短路径问题是通过加权匹配解决。在本文中,作为第一个与群无关的通解,我们提出了一个相当简单的,确定性的,强多项式时间算法的最短非零路问题。该算法基于Dijkstra的无约束最短路径问题算法和Edmonds的匹配算法中的花朵收缩技术;该方法受到Derigs的更快算法(1985)的启发,通过简化为加权匹配来解决奇偶约束最短路径问题。此外,我们改进了我们的算法,使它不需要显式的花收缩,并使计算时间匹配Derigs的。在加速步骤中,一个对偶线性规划的等价问题的基础上潜在的最大化的无约束最短路问题的制定起着关键作用。

英文摘要:

We study a constrained shortest path problem in group-labeled graphs with nonnegative edge length, called the shortest non-zero path problem. Depending on the group in question, this problem includes two types of tractable variants in undirected graphs: one is the parity-constrained shortest path/cycle problem, and the other is computing a shortest noncontractible cycle in surface-embedded graphs. For the shortest non-zero path problem with respect to finite abelian groups, Kobayashi and Toyooka (2017) proposed a randomized, pseudopolynomial-time algorithm via permanent computation. For a slightly more general class of groups, Yamaguchi (2016) showed a reduction of the problem to the weighted linear matroid parity problem. In particular, some cases are solved in strongly polynomial time via the reduction with the aid of a deterministic, polynomial-time algorithm for the weighted linear matroid parity problem developed by Iwata and Kobayashi (2021), which generalizes a well-known fact that the parity-constrained shortest path problem is solved via weighted matching. In this paper, as the first general solution independent of the group, we present a rather simple, deterministic, and strongly polynomial-time algorithm for the shortest non-zero path problem. The algorithm is based on Dijkstra's algorithm for the unconstrained shortest path problem and Edmonds' blossom shrinking technique in matching algorithms; this approach is inspired by Derigs' faster algorithm (1985) for the parity-constrained shortest path problem via a reduction to weighted matching. Furthermore, we improve our algorithm so that it does not require explicit blossom shrinking, and make the computational time match Derigs' one. In the speeding-up step, a dual linear programming formulation of the equivalent problem based on potential maximization for the unconstrained shortest path problem plays a key role.

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。

↑