Organizer(s):

Sepehr Assadi, Rutgers University

Swastik Kopparty, Rutgers University

Aaron Bernstein, Rutgers University

Abstract

In the decremental single-source shortest paths problem, the goal is to maintain distances from a fixed source s to every vertex v in a graph undergoing deletions. In this paper, we conclude a long line of research on this problem by showing a near-optimal deterministic data structure that maintains $(1+epsilon)$-approximate distance/path estimates and runs in $m^{1+o(1)}$ total update time. Our result, in particular, removes the oblivious adversary assumption required by the previous breakthrough result by Henzinger et al. FOCS'14], which leads to our second result: the first almost-linear time algorithm for $(1-epsilon)$-approximate min-cost flow in undirected graphs where capacities and costs can be taken over edges emph{and} vertices. Previously, algorithms for max flow with vertex capacities, or min-cost flow with any capacities required super-linear time. Our result essentially completes the picture for approximate flow in undirected graphs. The key technique of the first result is a novel framework that allows us to treat low-diameter graphs like expanders. This allows us to harness expander properties while bypassing shortcomings of expander decomposition, which almost all previous expander-based algorithms needed to deal with. For the second result, we break the notorious flow-decomposition barrier from the multiplicative-weight-update framework using randomization.

The Theory of Computing Seminar is being held online. Contact the organizers for the link to the seminar. 

See: https://sites.google.com/view/dimacs-theory-seminar/home