In the 2-Vertex-Connected Spanning Subgraph problem (2-VCSS), we are given an undirected graph $G$, and the objective is to find a 2-vertex-connected spanning subgraph $S$ of $G$ with the minimum number of edges. In the context of survivable network design, 2-VCSS is one of the most fundamental and well-studied problems. There has been active research on improving the approximation ratio of algorithms, and the current best ratio is $\frac{4}{3}$, achieved by Bosch-Calvo, Grandoni, and Jabal Ameli.In this paper, we improve the approximation ratio to $\frac{21}{16}+\varepsilon$ ($<1.313$). The key idea in our algorithm is to introduce a 2-edge-cover without certain cycle components, and use it as an initial solution.

翻译：暂无翻译