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arXiv 1804.01616math.CO
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有根树上的素Parking函数

Prime Parking Functions on Rooted Trees

Westin King, Catherine H. Yan

摘要:

对于一个标记的,有根树的边缘朝向根,我们认为顶点作为停车点和边缘方向作为一条单行道。每个司机,从她喜欢的停车位开始,沿着指向根的路径搜索并停在第一个未被占用的位置。如果所有$n$驾驶员都停车,则停车点偏好序列称为停车功能。我们考虑的序列,称为\emph{prime}停车功能,每个司机停车和树中的每个边缘是由一些司机后,未能在她的首选地点停车遍历。证明了树的顶点为$n$的素数停放函数的总数为$(2n-2)!$。此外,我们推广\emph{increasing}停车功能,其中的司机停车与弱增加的优先顺序,树和证明的总数量增加的素数停车功能的树与$n$顶点是$(n-1)!S_{n-1}$,其中$\{S_i\}_{i \geq 0}$是大Schröder数。

英文摘要:

For a labeled, rooted tree with edges oriented towards the root, we consider the vertices as parking spots and the edge orientation as a one-way street. Each driver, starting with her preferred parking spot, searches for and parks in the first unoccupied spot along the directed path to the root. If all $n$ drivers park, the sequence of spot preferences is called a parking function. We consider the sequences, called \emph{prime} parking functions, for which each driver parks and each edge in the tree is traversed by some driver after failing to park at her preferred spot. We prove that the total number of prime parking functions on trees with $n$ vertices is $(2n-2)!$. Additionally, we generalize \emph{increasing} parking functions, those in which the drivers park with a weakly-increasing order of preference, to trees and prove that the total number of increasing prime parking functions on trees with $n$ vertices is $(n-1)!S_{n-1}$, where $\{S_i\}_{i \geq 0}$ are the large Schröder numbers.

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