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.
@InProceedings{tu:LIPIcs.ISAAC.2022.63, author = {Tu, Ta-Wei}, title = {{Subquadratic Weighted Matroid Intersection Under Rank Oracles}}, booktitle = {33rd International Symposium on Algorithms and Computation (ISAAC 2022)}, pages = {63:1--63:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-258-7}, ISSN = {1868-8969}, year = {2022}, volume = {248}, editor = {Bae, Sang Won and Park, Heejin}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2022.63}, URN = {urn:nbn:de:0030-drops-173485}, doi = {10.4230/LIPIcs.ISAAC.2022.63}, annote = {Keywords: Matroids, Weighted Matroid Intersection, Combinatorial Optimization} }
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