Shortest Two Disjoint Paths in Conservative Graphs

Author Ildikó Schlotter

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Ildikó Schlotter
  • Centre for Economic and Regional Studies, Budapest, Hungary
  • Budapest University of Technology and Economics, Hungary

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Ildikó Schlotter. Shortest Two Disjoint Paths in Conservative Graphs. In 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 289, pp. 57:1-57:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


We consider the following problem that we call the Shortest Two Disjoint Paths problem: given an undirected graph G = (V,E) with edge weights w:E → ℝ, two terminals s and t in G, find two internally vertex-disjoint paths between s and t with minimum total weight. As shown recently by Schlotter and Sebő (2022), this problem becomes NP-hard if edges can have negative weights, even if the weight function is conservative, i.e., there are no cycles in G with negative total weight. We propose a polynomial-time algorithm that solves the Shortest Two Disjoint Paths problem for conservative weights in the case when the negative-weight edges form a constant number of trees in G.

Subject Classification

ACM Subject Classification
  • Theory of computation → Graph algorithms analysis
  • Theory of computation → Shortest paths
  • Theory of computation → Dynamic programming
  • Shortest paths
  • disjoint paths
  • conservative weights
  • graph algorithm


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