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Algorithmica

, Volume 13, Issue 5, pp 426–441 | Cite as

All-pairs shortest paths and the essential subgraph

  • C. C. McGeoch
Article

Abstract

The essential subgraph H of a weighted graph or digraphG contains an edge (v, w) if that edge is uniquely the least-cost path between its vertices. Let s denote the number of edges ofH. This paper presents an algorithm for solving all-pairs shortest paths onG that requires O(ns+n2 logn) worst-case running time. In general the time is equivalent to that of solvingn single-source problems using only edges inH. For general models of random graphs and digraphsG, s=0(n logn) almost surely. The subgraphH is optimal in the sense that it is the smallest subgraph sufficient for solving shortest-path problems inG. Lower bounds on the largest-cost edge ofH and on the diameter ofH andG are obtained for general randomly weighted graphs. Experimental results produce some new conjectures about essential subgraphs and distances in graphs with uniform edge costs.

Key words

All-pairs shortest path Single-source shortest path Random graph Random weighted graph Graph diameter Minimum spanning tree Essential arcs 

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Copyright information

© Springer-Verlag New York Inc 1995

Authors and Affiliations

  • C. C. McGeoch
    • 1
  1. 1.Department of Mathematics and Computer ScienceAmherst CollegeAmherstUSA

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