,
Guangting Chen
,
Mingyang Gong
,
Guohui Lin
,
An Zhang
Creative Commons Attribution 4.0 International license
We study the fair allocation of indivisible items to n agents to maximize the utilitarian social welfare, where the fairness criterion is envy-free up to one item and there are only two different utility functions shared by the agents. We present a 2-approximation algorithm when the two utility functions are normalized, improving the previous best ratio of 16 √n shown for general normalized utility functions; thus this constant ratio approximation algorithm confirms the APX-completeness in this special case previously shown APX-hard. When there are only three agents, i.e., n = 3, the previous best ratio is 3 shown for general utility functions, and we present an improved and tight 5/3-approximation algorithm when the two utility functions are normalized, and a best possible and tight 2-approximation algorithm when the two utility functions are unnormalized.
@InProceedings{ma_et_al:LIPIcs.ISAAC.2025.49,
author = {Ma, Jiaxuan and Chen, Yong and Chen, Guangting and Gong, Mingyang and Lin, Guohui and Zhang, An},
title = {{Maximizing Social Welfare Among EF1 Allocations at the Presence of Two Types of Agents}},
booktitle = {36th International Symposium on Algorithms and Computation (ISAAC 2025)},
pages = {49:1--49:19},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-408-6},
ISSN = {1868-8969},
year = {2025},
volume = {359},
editor = {Chen, Ho-Lin and Hon, Wing-Kai and Tsai, Meng-Tsung},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2025.49},
URN = {urn:nbn:de:0030-drops-249570},
doi = {10.4230/LIPIcs.ISAAC.2025.49},
annote = {Keywords: Fair allocation, utilitarian social welfare, envy-free up to one item, envy-cycle elimination, round robin, approximation algorithm}
}