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arXiv 2008.08417cs.DS
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模子集和、动态字符串与零和集合

Modular Subset Sum, Dynamic Strings, and Zero-Sum Sets

Jean Cardinal, John Iacono

AI总结:

本文提出了高概率O(m log m)时间的模子集和算法,利用动态字符串结构并提出更简单的Data Dependent Tree替代方案,同时给出了寻找Erdős-Ginzburg-Ziv定理零和子集的高概率O(n log n)时间算法。

摘要:

模子集和问题包括判定:给定模数 $m$、包含 $n$ 个取值在 $0..m-1$ 内的整数的多重集 $S$ 以及目标整数 $t$,是否存在 $S$ 的一个子集,其元素之和模 $m$ 等于 $t$,并在存在时报告这样的集合。我们为该问题提出了一个简单的高概率(w.h.p.)$O(m \log m)$ 时间算法。这构建在 Axiotis, Backurs, Jin, Tzamos 和 Wu (SODA 19) 先前的高概率 $O(m \log^7 m)$ 算法之上并进行了改进。我们的方法利用了 Gawrychowski 等人 (SODA 18) 动态字符串结构的 ADT。然而,由于该结构相当复杂,我们提出了一种更简单的替代方案,称为 Data Dependent Tree。作为应用,我们考虑了零和拉姆齐理论中一个基本定理的计算版本。Erdős-Ginzburg-Ziv 定理指出,包含 $2n - 1$ 个整数的多重集必定包含一个基数恰好为 $n$ 的子集,其值之和为 $n$ 的倍数。我们给出了一个高概率 $O(n \log n)$ 时间的算法来寻找这样的子集,改进了 Del Lungo, Marini 和 Mori (Disc. Math. 09) 的 $O(n^2)$ 算法。

英文摘要:

The modular subset sum problem consists of deciding, given a modulus $m$, a multiset $S$ of $n$ integers in $0..m-1$, and a target integer $t$, whether there exists a subset of $S$ with elements summing to $t \mod m $, and to report such a set if it exists. We give a simple $O(m \log m)$-time with high probability (w.h.p.) algorithm for the modular subset sum problem. This builds on and improves on a previous $O(m \log^7 m)$ w.h.p. algorithm from Axiotis, Backurs, Jin, Tzamos, and Wu (SODA 19). Our method utilizes the ADT of the dynamic strings structure of Gawrychowski et al. (SODA~18). However, as this structure is rather complicated we present a much simpler alternative which we call the Data Dependent Tree. As an application, we consider the computational version of a fundamental theorem in zero-sum Ramsey theory. The Erdős-Ginzburg-Ziv Theorem states that a multiset of $2n - 1$ integers always contains a subset of cardinality exactly $n$ whose values sum to a multiple of $n$. We give an algorithm for finding such a subset in time $O(n \log n)$ w.h.p. which improves on an $O(n^2)$ algorithm due to Del Lungo, Marini, and Mori (Disc. Math. 09).

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