An α-spanner of a graph G is a subgraph H such that H preserves all distances of G within a factor of α. In this paper, we give fully dynamic algorithms for maintaining a spanner H of a graph G undergoing edge insertions and deletions with worst-case guarantees on the running time after each update. In particular, our algorithms maintain: • a 3-spanner withÕ(n 1+1/2 ) edges with worst-case update timeÕ(n 3/4 ), or • a 5-spanner withÕ(n 1+1/3 ) edges with worst-case update timeÕ(n 5/9 ). These size/stretch tradeoffs are best possible (up to logarithmic factors). They can be extended to the weighted setting at very minor cost. Our algorithms are randomized and correct with high probability against an oblivious adversary. We also further extend our techniques to construct a 5-spanner with suboptimal size/stretch tradeoff, but improved worst-case update time. To the best of our knowledge, these are the first dynamic spanner algorithms with sublinear worst-case update time guarantees. Since it is known how to maintain a spanner using small amortized but large worst-case update time [Baswana et al. SODA'08], obtaining algorithms with strong worst-case bounds, as presented in this paper, seems to be the next natural step for this problem.
REF provided the first dynamic algorithms with sublinear worst-case update time for 3-spanners and 5-spanners.
Fully Dynamic Spanners with Worst-Case Update Time
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