Abstract
For an edge-weighted connected undirected graph, the minimum k-way cut problem is to find a subset of edges of minimum total weight whose removal separates the graph into k connected components. The problem is NP-hard when k is part of the input and W[1]-hard when k is taken as a parameter.
A simple algorithm for approximating a minimum k-way cut is to iteratively increase the number of components of the graph by h−1, where 2≤h≤k, until the graph has k components. The approximation ratio of this algorithm is known for h≤3 but is open for h≥4.
In this paper, we consider a general algorithm that successively increases the number of components of the graph by h i −1, where 2≤h 1≤h 2≤⋅⋅⋅≤h q and ∑ qi=1 (h i −1)=k−1. We prove that the approximation ratio of this general algorithm is \(2-(\sum_{i=1}^{q}{h_{i}\choose2})/{k\choose2}\) , which is tight. Our result implies that the approximation ratio of the simple iterative algorithm is 2−h/k+O(h 2/k 2) in general and 2−h/k if k−1 is a multiple of h−1.
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L. Cai was partially supported by Earmarked Research Grant 410206 of the Research Grants Council of Hong Kong SAR, China.
A.C.-C. Yao was partially supported by National Basic Research Program of China Grant 2007CB807900, 2007CB807901.
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Xiao, M., Cai, L. & Yao, A.CC. Tight Approximation Ratio of a General Greedy Splitting Algorithm for the Minimum k-Way Cut Problem. Algorithmica 59, 510–520 (2011). https://doi.org/10.1007/s00453-009-9316-1
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DOI: https://doi.org/10.1007/s00453-009-9316-1