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arXiv 1104.4081cs.DScs.GT
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关于拟阵秘书问题的变形

On Variants of the Matroid Secretary Problem

Shayan Oveis Gharan, Jan Vondrák

摘要:

我们提出了一些积极和消极的结果的变种拟阵秘书问题。最值得注意的是,我们设计了一个常数因子的竞争算法的“随机分配”模型的权重被随机分配给一个拟阵的元素,然后元素到达线上的对抗顺序(扩展的结果索托\cite{Soto11})。这是在假设拟阵是预先已知的情况下。如果拟阵是事先未知的,我们提出了一个$O(\log r \log n)$ -近似,并证明了一个更好的比$O(\log n / \log \log n)$近似是不可能的。这解决了Babaioff等人\cite{BIK07}提出的一个未决问题。作为一个自然的特殊情况下,我们还考虑了经典的秘书问题的候选人$n$的数量是事先未知的。如果$n$是从$\{1,...,N\}$的对手选择,我们提供了一个几乎紧的答案,通过提供一个算法,选择最佳的候选人与概率至少$1/(H_{N-1}+1)$,并证明了概率优于$1/H_N$不能实现(其中$H_N$是$N$ -th谐波数)。

英文摘要:

We present a number of positive and negative results for variants of the matroid secretary problem. Most notably, we design a constant-factor competitive algorithm for the "random assignment" model where the weights are assigned randomly to the elements of a matroid, and then the elements arrive on-line in an adversarial order (extending a result of Soto \cite{Soto11}). This is under the assumption that the matroid is known in advance. If the matroid is unknown in advance, we present an $O(\log r \log n)$-approximation, and prove that a better than $O(\log n / \log \log n)$ approximation is impossible. This resolves an open question posed by Babaioff et al. \cite{BIK07}. As a natural special case, we also consider the classical secretary problem where the number of candidates $n$ is unknown in advance. If $n$ is chosen by an adversary from $\{1,...,N\}$, we provide a nearly tight answer, by providing an algorithm that chooses the best candidate with probability at least $1/(H_{N-1}+1)$ and prove that a probability better than $1/H_N$ cannot be achieved (where $H_N$ is the $N$-th harmonic number).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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