Principles of organizing the interoperability of equipollent nodes in a wireless mesh-network with time division multiple access

Model. anal. inf. sist.

2019

In this paper, we study the two-step colouring problem for an undirected connected graph. It is required to colour the graph in a given number of colours in a way, when no pair of vertices has the same colour, if these vertices are at a distance of 1 or 2 between each other. Also the corresponding recognition problem is set. The problem is closely related to the classical graph colouring problem. In the article, we study and prove the polynomial reduction of the problems to each other. So it allows us to prove NP-completeness of the problem of two-step colouring. Also we specify some of its properties. Special interest is paid to the problem of two-step colouring in application to rectangular grid graphs. The maximum vertex degree in such a graph is between 0 and 4. For each case, we elaborate and prove the function of two-vertex colouring in the minimum possible number of colours. The functions allow each vertex to be coloured independently from others. If vertices are examined in a sequence, colouring time is polynomial for a rectangular grid graph.

unclassified

NP-completeness and One Polynomial Subclass of the Two-Step Graph Colouring Problem

Медведева

Model. anal. inf. sist.

2019

Two-Step Colouring of Grid Graphs of Different Types

Model. anal. inf. sist.

2022

In this article, we consider the NP-hard problem of the two-step colouring of a graph. It is required to colour the graph in a given number of colours in a way, when no pair of vertices has the same colour, if these vertices are at a distance of 1 or 2 between each other. The optimum two-step colouring is one that uses the minimum possible number of colours.The two-step colouring problem is studied in application to grid graphs. We consider four types of grids: triangular, square, hexagonal, and octogonal. We show that the optimum two-step colouring of hexagonal and octogonal grid graphs requires 4 colours in the general case. We formulate the polynomial algorithms for such a colouring. A square grid graph with the maximum vertex degree equal to 3 requires 4 or 5 colours for a two-step colouring. In the paper, we suggest the backtracking algorithm for this case. Also, we present the algorithm, which works in linear time relative to the number of vertices, for the two-step colouring in 7 colours of a triangular grid graph and show that this colouring is always correct. If the maximum vertex degree equals 6, the solution is optimum.

NP-Completeness and One Polynomial Subclass of the Two-Step Graph Colouring Problem

Medvedeva

Aut. Control Comp. Sci.

2020

Self Cite

Аннотация. В данной статье рассматривается задача о двухшаговой раскраске произвольного неориентированного связного графа. Она состоит в нахождении такой раскраски в заданное число цветов, при которой ни одна пара вершин на расстоянии 1 или 2 друг от друга не будет окрашена в одинаковый цвет. Также в работе ставится соответствующая задача распознавания.Данная задача тесно связана с классической задачей о раскраске графа. В статье рассматривается и обосновывается полиномиальное сведение задач друг к другу. В частности, это позволяет доказать NP-полноту задачи о двухшаговой раскраске. Кроме того, определяются некоторые ее свойства.Отдельно исследуется задача о двухшаговой раскраске в приложении к прямоугольным графам решетки. Максимальная степень вершины таких графов может принимать значение от 0 до 4, и для каждого возможного случая была определена и обоснована функция двухшаговой раскраски в минимальное число цветов. Полученные функции строятся таким образом, что каждая вершина графа может быть раскрашена независимо от остальных, а время раскраски прямоугольного графа решетки полиномиально при последовательном переборе вершин.