Path minima queries in dynamic weighted trees

  • Authors:
  • Gerth Stølting Brodal;Pooya Davoodi;S. Srinivasa Rao

  • Affiliations:
  • MADALGO, Department of Computer Science, Aarhus University;MADALGO, Department of Computer Science, Aarhus University;School of Computer Science and Engineering, Seoul National University, S. Korea

  • Venue:
  • WADS'11 Proceedings of the 12th international conference on Algorithms and data structures
  • Year:
  • 2011

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Abstract

In the path minima problem on trees each tree edge is assigned a weight and a query asks for the edge with minimum weight on a path between two nodes. For the dynamic version of the problem on a tree, where the edge-weights can be updated, we give comparison-based and RAM data structures that achieve optimal query time. These structures support inserting a node on an edge, inserting a leaf, and contracting edges. When only insertion and deletion of leaves in a tree are needed, we give two data structures that achieve optimal and significantly lower query times than when updating the edge-weights is allowed. One is a semigroup structure for which the edge-weights are from an arbitrary semigroup and queries ask for the semigroup-sum of the edge-weights on a given path. For the other structure the edge-weights are given in the word RAM. We complement these upper bounds with lower bounds for different variants of the problem.