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| Content Provider | Society for Industrial and Applied Mathematics (SIAM) |
|---|---|
| Author | Nutov, Zeev Kortsarz, Guy Cygan, Marek |
| Copyright Year | 2013 |
| Abstract | We consider connectivity problems with orientation constraints. Given a directed graph $D$ and a collection of ordered node pairs $P$ let $P[D]=\{(u,v) \in P: D \mbox{ contains a } uv\mbox{-path}\}$. In the \sf Steiner Forest Orientation problem we are given an undirected graph $G=(V,E)$ with edge-costs and a set $P \subseteq V \times V$ of ordered node pairs. The goal is to find a minimum-cost subgraph $H$ of $G$ and an orientation $D$ of $H$ such that $P[D]=P$. We give a $4$-approximation algorithm for this problem. In the \sf Maximum Pairs Orientation problem we are given a graph $G$ and a multicollection of ordered node pairs $P$ on $V$. The goal is to find an orientation $D$ of $G$ such that $|P[D]|$ is maximum. Generalizing the result of Arkin and Hassin [Discrete Appl. Math., 116 (2002), pp. 271--278] for $|P|=2$, we will show that for a mixed graph $G$ (that may have both directed and undirected edges), one can decide in $n^{O(|P|)}$ time whether $G$ has an orientation $D$ with $P[D]=P$. (For undirected graphs this problem admits a polynomial time algorithm for any $P$, but it is NP-complete on mixed graphs.) For undirected graphs, we will show that one can decide whether $G$ admits an orientation $D$ with $|P[D]| \geq k$ in $O(n+m)+2^{O(k\cdot \log \log k)}$ time; hence this decision problem is fixed-parameter tractable, which answers an open question from Dorn et al. [Algorithms Molecular Biol., 6 (2011)]. We also show that \sf Maximum Pairs Orientation admits ratio $O(\log |P|/\log\log |P|)$, which is better than the ratio $O(\log n/\log\log n)$ of Gamzu, Segev, and Sharan [Proceedings of WABI 2010, pp. 215--225] when $|P| |
| Starting Page | 1503 |
| Ending Page | 1513 |
| Page Count | 11 |
| File Format | |
| ISSN | 08954801 |
| DOI | 10.1137/120883931 |
| e-ISSN | 10957146 |
| Journal | SIAM Journal on Discrete Mathematics (SJDMEC) |
| Issue Number | 3 |
| Volume Number | 27 |
| Language | English |
| Publisher | Society for Industrial and Applied Mathematics |
| Publisher Date | 2013-09-12 |
| Access Restriction | Subscribed |
| Subject Keyword | Nonnumerical algorithms Analysis of algorithms and problem complexity graph orientation parameterized complexity Graph theory approximation algorithms Graph algorithms Analysis of algorithms graph algorithms |
| Content Type | Text |
| Resource Type | Article |
| Subject | Mathematics |
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