Online carpooling against an oblivious adversary
Abstract
In the online carpooling problem, edges on n vertices arrive one at a time and must be oriented immediately, so as to keep the difference between the indegree and the outdegree of every vertex small. We give a randomized online algorithm which bounds the largest absolute difference over the first T edges by O((log T)1/3) with high probability on every input sequence fixed in advance. This proves a conjecture of Kulkarni, Reis and Rothvoss and matches the known worst case lower bound. The algorithm keeps the law of the discrepancy vector dominated in the convex order by a Gaussian measure, and forces the endpoint with the smaller discrepancy to receive the edge whenever the two discrepancies are far apart. In the analysis we show that a vertex of discrepancy D is preceded by a set of O(D) vertices with total discrepancy Ω(D2).
Related
BibTeX
@misc{lei2026online,
title = {{Online carpooling against an oblivious adversary}},
author = {Yuhao Lei},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.00388},
eprint = {2611.00388},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.00388},
}
RIS
TY - UNPB
TI - Online carpooling against an oblivious adversary
AU - Yuhao Lei
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2611.00388
UR - https://arxiv.org/abs/2611.00388
AB - In the online carpooling problem, edges on n vertices arrive one at a time and must be oriented immediately, so as to keep the difference between the indegree and the outdegree of every vertex small. We give a randomized online algorithm which bounds the largest absolute difference over the first T edges by O((log T)^1/3) with high probability on every input sequence fixed in advance. This proves a conjecture of Kulkarni, Reis and Rothvoss and matches the known worst case lower bound. The algorithm keeps the law of the discrepancy vector dominated in the convex order by a Gaussian measure, and forces the endpoint with the smaller discrepancy to receive the edge whenever the two discrepancies are far apart. In the analysis we show that a vertex of discrepancy D is preceded by a set of O(D) vertices with total discrepancy Ω(D^2).
ER -