,
Ryan Williams
,
Stan Zhang
Creative Commons Attribution 4.0 International license
We study the Pigeonhole Equal Subset Sum problem, which is a total-search variant of the Subset Sum problem introduced by Papadimitriou (1994): we are given a set of n positive integers {w₁,…,w_n} with the additional restriction that ∑_{i=1}^n w_i < 2ⁿ - 1, and want to find two different subsets A,B ⊆ [n] such that ∑_{i∈A} w_i = ∑_{i∈B} w_i.
Very recently, Jin and Wu (ICALP 2024) gave a randomized algorithm solving Pigeonhole Equal Subset Sum in O^*(2^{0.4n}) time, beating the classical meet-in-the-middle algorithm with O^*(2^{n/2}) runtime. In this paper, we refine Jin and Wu’s techniques to improve the runtime even further to O^*(2^{n/3}).
@InProceedings{jin_et_al:LIPIcs.ESA.2025.86,
author = {Jin, Ce and Williams, Ryan and Zhang, Stan},
title = {{New Algorithms for Pigeonhole Equal Subset Sum}},
booktitle = {33rd Annual European Symposium on Algorithms (ESA 2025)},
pages = {86:1--86:12},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-395-9},
ISSN = {1868-8969},
year = {2025},
volume = {351},
editor = {Benoit, Anne and Kaplan, Haim and Wild, Sebastian and Herman, Grzegorz},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2025.86},
URN = {urn:nbn:de:0030-drops-245541},
doi = {10.4230/LIPIcs.ESA.2025.86},
annote = {Keywords: pigeonhole principle, subset sums}
}