Optimal Offline Dynamic \(2,3\)-Edge/Vertex Connectivity

We give offline algorithms for processing a sequence of \(2\) and \(3\) edge and vertex connectivity queries in a fully-dynamic undirected graph. While the current best fully-dynamic online data structures for \(3\)-edge and \(3\)-vertex connectivity require \(O(n^{2/3})\) and \(O(n)\) time per update, respectively, our per-operation cost is only \(O(\log n)\), optimal due to the dynamic connectivity lower bound of Patrascu and Demaine. Our approach utilizes a divide and conquer scheme that transforms a graph into smaller equivalents that preserve connectivity information. This construction of equivalents is closely-related to the development of vertex sparsifiers, and shares important connections to several upcoming results in dynamic graph data structures, outside of just the offline model.