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arXiv · 2604.12653

Sorting under Partial Information with Optimal Preprocessing Time via Unified Bound Heaps

Daniel Rutschmann
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Abstract

In 1972, Fredman proposes the problem of sorting under partial information: preprocess a directed acyclic graph $G$ with vertex set $X$ so that you can sort $X$ in $O(\log e(G))$ time, where $e(G)$ is the number of sorted orders compatible with $G$. Cardinal, Fiorini, Joret, Jungers and Munro [STOC'10] show that you can preprocess $G$ in $O(n^{2.5})$ time and then sort $X$ in $O(\log e(G) + n)$ time and $O(\log e(G))$ comparisons. Recent work of van der Hoog and Rutschmann [FOCS'24] implies an algorithm with $O(n^ω)$ preprocessing time where $ω< 2.372$ and $O(\log e(G))$ sorting time. Haeupler, Hladík, Iacono, Rozhoň, Tarjan and Tětek [SODA'25] achieve an overall running time of $O(\log e(G) + m)$. In this paper, we achieve tight bounds for this problem: $O(m)$ preprocessing time and $O(\log e(G))$ sorting time. As a key ingredient, we design a new fast heap data structure that might be of independent theoretical interest.

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Daniel Rutschmann. 2026-04-14. Sorting under Partial Information with Optimal Preprocessing Time via Unified Bound Heaps. https://arxiv.org/abs/2604.12653

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