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A threshold of ln n for approximating set cover

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Feige, Uriel·1998·Journal of the ACM

Abstract

Given a collection ℱ of subsets of S = {1,…, n }, set cover is the problem of selecting as few as possible subsets from ℱ such that their union covers S, , and max k-cover is the problem of selecting k subsets from ℱ such that their union has maximum cardinality. Both these problems are NP-hard. We prove that (1 - o (1)) ln n is a threshold below which set cover cannot be approximated efficiently, unless NP has slightly superpolynomial time algorithms. This closes the gap (up to low-order terms) between the ratio of approximation achievable by the greedy alogorithm (which is (1 - o (1)) ln n), and provious results of Lund and Yanakakis, that showed hardness of approximation within a ratio of (log 2 n ) / 2 ≃0.72 ln n . For max k -cover, we show an approximation threshold of (1 - 1/ e )(up to low-order terms), under assumption that P ≠ NP .

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Metadata

Authors
Feige, U.
Venue
Journal of the ACM
Published
1998-07
Volume
45
Issue
4
Pages
634-652
ISSN
  • 0004-5411 (ISSN-L)
  • 1557-735X
OpenAlex
W2143996311
Cited by
3,086
References
1
FWCI
41.68
Type
journal article
Language
en
Open access
bronze

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CoChat. (2026). Citation check: A threshold of ln n for approximating set cover. https://app.cochat.ai/papers/10.1145/285055.285059
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Feige, U. (1998). A threshold of ln n for approximating set cover. Journal of the ACM. https://doi.org/10.1145/285055.285059

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