English

Improved approximation algorithms for some capacitated $k$ edge connectivity problems

Data Structures and Algorithms 2023-07-06 v1

Abstract

We consider the following two variants of the Capacitated kk-Edge Connected Subgraph} (Cap-k-ECS) problem. Near Min-Cuts Cover: Given a graph G=(V,E)G=(V,E) with edge costs and E0EE_0 \subseteq E, find a min-cost edge set JEE0J \subseteq E \setminus E_0 that covers all cuts with at most k1k-1 edges of the graph G0=(V,E0)G_0=(V,E_0). We obtain approximation ratio kλ0+1+ϵk-\lambda_0+1+\epsilon, improving the ratio 2min{kλ0,8}2\min\{k-\lambda_0,8\} of Bansal, Cheriyan, Grout, and Ibrahimpur for kλ014k-\lambda_0 \leq 14,where λ0\lambda_0 is the edge connectivity of G0G_0. (k,q)(k,q)-Flexible Graph Connectivity ((k,q)(k,q)-FGC): Given a graph G=(V,E)G=(V,E) with edge costs and a set UEU \subseteq E of ''unsafe'' edges and integers k,qk,q, find a min-cost subgraph HH of GG such that every cut of HH has at least kk safe edges or at least k+qk+q edges. We show that (k,1)(k,1)-FGC admits approximation ratio 3.5+ϵ3.5+\epsilon if kk is odd (improving the previous ratio 44), and that (k,2)(k,2)-FGC admits approximation ratio 66 if kk is even and 7+ϵ7+\epsilon if kk is odd (improving the previous ratio 2020).

Keywords

Cite

@article{arxiv.2307.01650,
  title  = {Improved approximation algorithms for some capacitated $k$ edge connectivity problems},
  author = {Zeev Nutov},
  journal= {arXiv preprint arXiv:2307.01650},
  year   = {2023}
}