Lecture Notes in Computer Science, 1999, Volume 1627/1999, 164-173, DOI: 10.1007/3-540-48686-0_16

A Faster Algorithm for Computing Minimum 5-Way and 6-Way Cuts in Graphs

Hiroshi Nagamochi, Shigeki Katayama and Toshihide Ibaraki

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Abstract

For an edge-weighted graph G with n vertices and m edges, the minimum k-way cut problem is to find a partition of the vertex set into k non-empty subsets so that the weight sum of edges between different subsets is minimized. For this problem with k = 5 and 6, we present a deterministic algorithm that runs in $ O\left( {n^{k - 2} \left( {nF\left( {n,m} \right) + C_2 \left( {n,m} \right) + n^2 } \right)} \right) = O\left( {mn^k \log \left( {n^2 /m} \right)} \right) $ O\left( {n^{k - 2} \left( {nF\left( {n,m} \right) + C_2 \left( {n,m} \right) + n^2 } \right)} \right) = O\left( {mn^k \log \left( {n^2 /m} \right)} \right) time, where F(n,m) and C 2 (n,m) denote respectively the time bounds required to solve the maximum flow problem and the minimum 2-way cut problem in G. The bounds $ \tilde O\left( {mn^5 } \right) $ \tilde O\left( {mn^5 } \right) for k = 5 and $ \tilde O\left( {mn^6 } \right) $ \tilde O\left( {mn^6 } \right) for k = 6 improve the previous best randomized bounds $ \tilde O\left( {n^8 } \right) $ \tilde O\left( {n^8 } \right) and $ \tilde O\left( {n^{10} } \right) $ \tilde O\left( {n^{10} } \right) , respectively.
This research was partially supported by the Scientific Grant-in-Aid from Ministry of Education, Science, Sports and Culture of Japan, and the subsidy from the Inamori Foundation.

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