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Graph coloring with preferences offers a powerful framework for constraint satisfaction problems in which fulfilling every request is impossible but satisfying a guaranteed positive fraction is highly desirable. A \emph{request} on a graph…

Combinatorics · Mathematics 2026-05-25 Shu Fang , Runrun Liu , Gexin Yu

In the flexible list coloring problem, we consider a graph $G$ and a color list assignment $L$ on $G$, as well as a subset $U \subseteq V(G)$ for which each $u \in U$ has a preferred color $p(u) \in L(u)$. Our goal is to find a proper…

Combinatorics · Mathematics 2025-01-29 Richard Bi , Peter Bradshaw

Flexible list coloring was introduced by Dvo\v{r}\'{a}k, Norin, and Postle in 2019. Suppose $0 \leq \epsilon \leq 1$, $G$ is a graph, $L$ is a list assignment for $G$, and $r$ is a function with non-empty domain $D\subseteq V(G)$ such that…

Combinatorics · Mathematics 2024-02-21 Hemanshu Kaul , Rogers Mathew , Jeffrey A. Mudrock , Michael J. Pelsmajer

For a given $\varepsilon > 0$, we say that a graph $G$ is $\varepsilon$-flexibly $k$-choosable if the following holds: for any assignment $L$ of color lists of size $k$ on $V(G)$, if a preferred color from a list is requested at any set $R$…

Combinatorics · Mathematics 2023-06-13 Peter Bradshaw , Tomáš Masařík , Ladislav Stacho

Suppose $G$ is a graph and $L$ is a list assignment for $G$. A request of $L$ is a function $r$ with nonempty domain $D\subseteq V(G)$ such that $r(v) \in L(v)$ for each $v \in D$. The triple $(G,L,r)$ is $\epsilon$-satisfiable if there…

We consider the flexible list coloring problem, in which we have a graph $G$, a color list assignment $L:V(G) \rightarrow 2^{\mathbb N}$, and a set $U \subseteq V(G)$ of vertices such that each $u \in U$ has a preferred color $p(u) \in…

Combinatorics · Mathematics 2024-08-19 Richard Bi , Peter Bradshaw

The concept of DP-coloring of a graph is a generalization of list coloring introduced by Dvo\v{r}\'{a}k and Postle in 2015. Multiple DP-coloring of graphs, as a generalization of multiple list coloring, was first studied by Bernshteyn,…

Combinatorics · Mathematics 2022-01-31 Huan Zhou , Xuding Zhu

Given a graph $G$ and a mapping $f:V(G) \to \mathbb{N}$, an $f$-list assignment of $G$ is a function that maps each $v \in V(G)$ to a set of at least $f(v)$ colors. For an $f$-list assignment $L$ of a graph $G$, a proper conflict-free…

Combinatorics · Mathematics 2026-01-23 Masaki Kashima , Riste Škrekovski , Rongxing Xu

Proper graph coloring assigns different colors to adjacent vertices of the graph. Usually, the number of colors is fixed or as small as possible. Consider applications (e.g. variants of scheduling) where colors represent limited resources…

Combinatorics · Mathematics 2019-09-10 Tomáš Masařík

Recently, Dvo\v{r}\'ak, Norin, and Postle introduced flexibility as an extension of list coloring on graphs [JGT 19']. In this new setting, each vertex $v$ in some subset of $V(G)$ has a request for a certain color $r(v)$ in its list of…

Combinatorics · Mathematics 2023-06-13 Bernard Lidický , Tomáš Masařík , Kyle Murphy , Shira Zerbib

DP-coloring (also known as correspondence coloring) is a generalization of list coloring developed recently by Dvo\v{r}\'{a}k and Postle. In this paper we introduce and study the fractional DP-chromatic number $\chi_{DP}^\ast(G)$. We…

Combinatorics · Mathematics 2019-06-04 Anton Bernshteyn , Alexandr Kostochka , Xuding Zhu

DP-coloring (also known as correspondence coloring) is a generalization of list coloring developed recently by Dvorak and Postle. We introduce and study $(i,j)$-defective DP-colorings of multigraphs. We concentrate on sparse multigraphs and…

Combinatorics · Mathematics 2019-12-10 Yifan Jing , Alexandr Kostochka , Fuhong Ma , Pongpat Sittitrai , Jingwei Xu

A graph where each vertex $v$ has a list $L(v)$ of available colors is $L$-colorable if there is a proper coloring such that the color of $v$ is in $L(v)$ for each $v$. A graph is $k$-choosable if every assignment $L$ of at least $k$ colors…

Discrete Mathematics · Computer Science 2021-10-26 Ilkyoo Choi , Felix Christian Clemen , Michael Ferrara , Paul Horn , Fuhong Ma , Tomáš Masařík

A proper coloring of a graph is \emph{conflict-free} if, for every non-isolated vertex, some color is used exactly once on its neighborhood. Caro, Petru\v{s}evski, and \v{S}krekovski proved that every graph $G$ has a proper conflict-free…

Combinatorics · Mathematics 2024-12-16 Daniel W. Cranston , Chun-Hung Liu

DP-coloring (or correspondence coloring) is a generalization of list coloring that has been widely studied since its introduction by Dvo\v{r}\'{a}k and Postle in 2015. As the analogue of the chromatic polynomial of a graph $G$, $P(G,m)$,…

Combinatorics · Mathematics 2023-03-21 Samantha L. Dahlberg , Hemanshu Kaul , Jeffrey A. Mudrock

A proper vertex coloring of a graph is equitable if the sizes of all color classes differ by at most $1$. For a list assignment $L$ of $k$ colors to each vertex of an $n$-vertex graph $G$, an equitable $L$-coloring of $G$ is a proper…

Combinatorics · Mathematics 2025-12-30 H. A. Kierstead , Alexandr Kostochka , Zimu Xiang

A generalization of list-coloring, now known as DP-coloring, was recently introduced by Dvo\v{r}\'{a}k and Postle. Essentially, DP-coloring assigns an arbitrary matching between lists of colors at adjacent vertices, as opposed to only…

Combinatorics · Mathematics 2018-09-21 Runrun Liu , Sarah Loeb , Martin Rolek , Yuxue Yin , Gexin Yu

One of Thomassen's classical results is that every planar graph of girth at least $5$ is 3-choosable. One can wonder if for a planar graph $G$ of girth sufficiently large and a $3$-list-assignment $L$, one can do even better. Can one find…

Combinatorics · Mathematics 2023-12-29 Stijn Cambie , Wouter Cames van Batenburg , Xuding Zhu

A {\it dynamic $k$-coloring} of a graph $G$ is a proper $k$-coloring of the vertices of $G$ such that every vertex of degree at least 2 in $G$ will be adjacent to vertices with at least 2 different colors. The smallest number $k$ for which…

Discrete Mathematics · Computer Science 2007-11-20 Xueliang Li , Wenli Zhou

While solving a question on list coloring of planar graphs, Dvo\v{r}\'{a}k and Postle introduced the new notion of DP-coloring (they called it correspondence coloring). A DP-coloring of a graph $G$ reduces the problem of finding a coloring…

Combinatorics · Mathematics 2018-03-26 Anton Bernshteyn , Alexandr Kostochka , Sergei Pron
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