作者: Michel X. Goemans , Harold N. Gabow , Éva Tardos , David P. Williamson
DOI: 10.1002/NET.V53:4
关键词: Multigraph 、 Discrete mathematics 、 Connectivity 、 Graph (abstract data type) 、 Mathematics 、 Approximation algorithm 、 Directed graph 、 Upper and lower bounds 、 Round-off error 、 Combinatorics 、 Rounding
摘要: The smallest k-ECSS problem is, given a graph along with an integer k, find spanning subgraph that is k-edge connected and contains the fewest possible number of edges. We examine natural approximation algorithm based on rounding LP solution. A tight bound ratio 1 + 3-k for undirected graphs k > odd, 2-k even, directed arbitrary. Using iterated improves first upper to 2-k. On hardness side we show some absolute constant c 0, any ≥ 2 (k 1), polynomial-time approximating (directed) multigraphs within c-k would imply P = NP. © 2008 Wiley Periodicals, Inc. NETWORKS, 2009