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Approximability of packing disjoint cycles. (English) Zbl 1193.68286
Tokuyama, Takeshi (ed.), Algorithms and computation. 18th international symposium, ISAAC 2007, Sendai, Japan, December 17–19, 2007. Proceedings. Berlin: Springer (ISBN 978-3-540-77118-0/pbk). Lecture Notes in Computer Science 4835, 304-315 (2007).
Summary: Given a graph $$G$$, the edge-disjoint cycle packing problem is to find the largest set of cycles of which no two share an edge. For undirected graphs, the best known approximation algorithm has ratio $$O(\sqrt{\log n})$$. In fact, the same upper bound was proved for the integrality gap of this problem by presenting a simple greedy algorithm. Here we show that this is almost best possible. By modifying integrality gap and hardness results for the edge-disjoint paths problem, we show that the undirected edge-disjoint cycle packing problem has an integrality gap of $$\Omega(\frac{\sqrt{\log n}}{\log\log n})$$ and furthermore it is quasi-NP-hard to approximate the edge-disjoint cycle problem within ratio of $$O(\log^{\frac{1}{2}-\epsilon} n)$$ for any constant $$\epsilon > 0$$. The same results hold for the problem of packing vertex-disjoint cycles.
For the entire collection see [Zbl 1136.68011].

MSC:
 68W25 Approximation algorithms 05B40 Combinatorial aspects of packing and covering 05C38 Paths and cycles 05C85 Graph algorithms (graph-theoretic aspects) 68Q17 Computational difficulty of problems (lower bounds, completeness, difficulty of approximation, etc.)
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