All-pairs shortest paths in O(n2) time with high probability

  • Authors:
  • Yuval Peres;Dmitry Sotnikov;Benny Sudakov;Uri Zwick

  • Affiliations:
  • Microsoft Research, Redmond, WA;Tel Aviv University, Tel Aviv, Israel;University of California, Los Angeles, CA;Tel Aviv University, Tel Aviv, Israel

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 2013

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Abstract

We present an all-pairs shortest path algorithm whose running time on a complete directed graph on n vertices whose edge weights are chosen independently and uniformly at random from [0,1] is O(n2), in expectation and with high probability. This resolves a long-standing open problem. The algorithm is a variant of the dynamic all-pairs shortest paths algorithm of Demetrescu and Italiano [2006]. The analysis relies on a proof that the number of locally shortest paths in such randomly weighted graphs is O(n2), in expectation and with high probability. We also present a dynamic version of the algorithm that recomputes all shortest paths after a random edge update in O(log2n) expected time.