Minimum Cut of Directed Planar Graphs in O(n log log n) Time

Abstract

We give an O(n log log n) time algorithm for computing the minimum cut (or equivalently, the shortest cycle) of a weighted directed planar graph. This improves the previous fastest O(n log3 n) solution. Interestingly, while in undirected planar graphs both min cut and min st-cut have O(n log log n) solutions, in directed planar graphs our result makes min cut faster than min st-cut, which currently requires O(n log n).