Subquadratic Weighted Matroid Intersection Under Rank Oracles

Author Ta-Wei Tu

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Ta-Wei Tu
  • National Taiwan University, Taipei, Taiwan


I would like to thank Prof. Hsueh-I Lu for advising the project and helpful suggestions on the writing and notation. I also thank Min-Yen Tsai for proof-reading an initial draft of this paper and the anonymous reviewers of ISAAC 2022 for their useful comments.

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Ta-Wei Tu. Subquadratic Weighted Matroid Intersection Under Rank Oracles. In 33rd International Symposium on Algorithms and Computation (ISAAC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 248, pp. 63:1-63:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


Given two matroids ℳ₁ = (V, ℐ₁) and ℳ₂ = (V, ℐ₂) over an n-element integer-weighted ground set V, the weighted matroid intersection problem aims to find a common independent set S^* ∈ ℐ₁ ∩ ℐ₂ maximizing the weight of S^*. In this paper, we present a simple deterministic algorithm for weighted matroid intersection using Õ(nr^{3/4} log{W}) rank queries, where r is the size of the largest intersection of ℳ₁ and ℳ₂ and W is the maximum weight. This improves upon the best previously known Õ(nr log{W}) algorithm given by Lee, Sidford, and Wong [FOCS'15], and is the first subquadratic algorithm for polynomially-bounded weights under the standard independence or rank oracle models. The main contribution of this paper is an efficient algorithm that computes shortest-path trees in weighted exchange graphs.

Subject Classification

ACM Subject Classification
  • Theory of computation → Discrete optimization
  • Mathematics of computing → Combinatorial optimization
  • Mathematics of computing → Matroids and greedoids
  • Matroids
  • Weighted Matroid Intersection
  • Combinatorial Optimization


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