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In this paper, we study the performance of the FirstFit algorithm for the online unit-length intervals coloring problem where the intervals can be either open or closed, which serves a further investigation towards the actual performance of…

Data Structures and Algorithms · Computer Science 2025-02-11 Bob Krekelberg , Alison Hsiang-Hsuan Liu

Recently, it was proved that triangle-free intersection graphs of $n$ line segments in the plane can have chromatic number as large as $\Theta(\log\log n)$. Essentially the same construction produces $\Theta(\log\log n)$-chromatic…

Computational Geometry · Computer Science 2014-12-30 Tomasz Krawczyk , Arkadiusz Pawlik , Bartosz Walczak

A conflict-free open neighborhood coloring of a graph is an assignment of colors to the vertices such that for every vertex there is a color that appears exactly once in its open neighborhood. For a graph $G$, the smallest number of colors…

Combinatorics · Mathematics 2025-11-11 Sriram Bhyravarapu , Shiwali Gupta , Subrahmanyam Kalyanasundaram , Rogers Mathew

Given a graph, the conflict-free coloring problem on open neighborhoods (CFON) asks to color the vertices of the graph so that all the vertices have a uniquely colored vertex in its open neighborhood. The smallest number of colors required…

Combinatorics · Mathematics 2020-09-16 Sriram Bhyravarapu , Subrahmanyam Kalyanasundaram , Rogers Mathew

We study the problem of colouring the vertices of a polygon, such that every viewer in it can see a unique colour. The goal is to minimise the number of colours used. This is also known as the conflict-free chromatic guarding problem with…

Computational Geometry · Computer Science 2020-04-07 Onur Çağırıcı , Subir Kumar Ghosh , Petr Hliněný , Bodhayan Roy

Given a geometric hypergraph (or a range-space) $H=(V,\cal E)$, a coloring of its vertices is said to be conflict-free if for every hyperedge $S \in \cal E$ there is at least one vertex in $S$ whose color is distinct from the colors of all…

Combinatorics · Mathematics 2010-12-14 Panagiotis Cheilaris , Shakhar Smorodinsky , Marek Sulovský

An edge-coloring of a graph $G$ with colors $1,...,t$ is an interval $t$-coloring if all colors are used, and the colors of edges incident to each vertex of $G$ are distinct and form an interval of integers. A graph $G$ is interval…

Combinatorics · Mathematics 2012-02-02 Petros A. Petrosyan , Hrant H. Khachatrian , Hovhannes G. Tananyan

In this paper, we settle the open complexity status of interval constrained coloring with a fixed number of colors. We prove that the problem is already NP-complete if the number of different colors is 3. Previously, it has only been known…

Discrete Mathematics · Computer Science 2009-12-17 Jaroslaw Byrka , Andreas Karrenbauer , Laura Sanita

We introduce peaceful colourings, a variant of $h$-conflict free colourings. We call a colouring with no monochromatic edges $p$-peaceful if for each vertex $v$, there are at most $p$ neighbours of $v$ coloured with a colour appearing on…

Combinatorics · Mathematics 2025-08-22 Chun-Hung Liu , Bruce Reed

An edge-coloring of a multigraph $G$ with colors $1,\ldots,t$ is called an interval $t$-coloring if all colors are used, and the colors of edges incident to any vertex of $G$ are distinct and form an interval of integers. In this note, we…

Combinatorics · Mathematics 2013-11-19 Petros A. Petrosyan

We study the online graph coloring problem restricted to the intersection graphs of intervals with lengths in $[1,\sigma]$. For $\sigma=1$ it is the class of unit interval graphs, and for $\sigma=\infty$ the class of all interval graphs.…

The closed neighborhood conflict-free chromatic number of a graph $G$, denoted by $\chi_{CN}(G)$, is the minimum number of colors required to color the vertices of $G$ such that for every vertex, there is a color that appears exactly once…

Combinatorics · Mathematics 2021-03-10 Sriram Bhyravarapu , Subrahmanyam Kalyanasundaram , Rogers Mathew

There is a huge difference in techniques and runtimes of distributed algorithms for problems that can be solved by a sequential greedy algorithm and those that cannot. A prime example of this contrast appears in the edge coloring problem:…

Data Structures and Algorithms · Computer Science 2025-05-27 Manuel Jakob , Yannic Maus , Florian Schager

We design fast dynamic algorithms for proper vertex and edge colorings in a graph undergoing edge insertions and deletions. In the static setting, there are simple linear time algorithms for $(\Delta+1)$- vertex coloring and…

Data Structures and Algorithms · Computer Science 2017-11-15 Sayan Bhattacharya , Deeparnab Chakrabarty , Monika Henzinger , Danupon Nanongkai

We consider a coloring problem on dynamic, one-dimensional point sets: points appearing and disappearing on a line at given times. We wish to color them with k colors so that at any time, any sequence of p(k) consecutive points, for some…

Identifying the sets of operations that can be executed simultaneously is an important problem appearing in many parallel applications. By modeling the operations and their interactions as a graph, one can identify the independent…

Distributed, Parallel, and Cluster Computing · Computer Science 2014-07-28 Ahmet Erdem Sarıyüce , Erik Saule , Ümit V. Çatalyürek

A proper vertex colouring of a graph $G$ is referred to as conflict-free if in the neighbourhood of every vertex some colour appears exactly once, while it is called $h$-conflict-free if there are at least $h$ such colours for each vertex…

Combinatorics · Mathematics 2022-12-20 Mateusz Kamyczura , Jakub Przybyło

The main goal of this paper is to formalize and explore a connection between chromatic properties of graphs with geometric representations and competitive analysis of on-line algorithms, which became apparent after the recent construction…

Data Structures and Algorithms · Computer Science 2016-12-30 Tomasz Krawczyk , Bartosz Walczak

An \emph{interval $t$-coloring} of a graph $G$ is a proper edge-coloring with colors $1,\dots,t$ such that the colors on the edges incident to every vertex of $G$ are colored by consecutive colors. A graph $G$ is called \emph{interval…

Combinatorics · Mathematics 2024-09-27 Petros A. Petrosyan , Hrant H. Khachatrian , Hovhannes G. Tananyan

Reconfiguration problems ask whether one feasible solution can be transformed into another by a sequence of local moves while maintaining feasibility throughout. For integers $d \geq 1$ and $k \geq d+1$, the Distance Coloring problem asks…

Data Structures and Algorithms · Computer Science 2026-05-19 Niranka Banerjee , Christian Engels , Duc A. Hoang