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3. Vertex and Edge Colouring

The lecture focuses on vertex and edge colouring in graph theory, emphasizing their applications such as exam scheduling and tournament match planning. It explains the concepts of vertex chromatic number and edge chromatic number, along with greedy algorithms for colouring. The complexities and challenges associated with finding the chromatic numbers are highlighted, alongside upper and lower bounds on these values.

Sections

Vertex and Edge Colouring

This section introduces vertex and edge colouring in graph theory, along with their practical applications and challenges.

3 Section Overview

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3.1.1 Vertex Colouring Motivation

This section explores the motivation behind vertex colouring problems using practical examples such as exam scheduling.

3.1.2 Vertex Colouring Problem

The vertex colouring problem involves assigning colors to graph vertices such that no two adjacent vertices share the same color, with real-world applications such as exam scheduling.

3.1.3 Vertex Chromatic Number

The section introduces the vertex chromatic number, focusing on its definition, significance in graph theory, and practical applications in problems like exam scheduling.

3.1.4 Greedy Algorithm for Vertex Colouring

This section discusses the greedy algorithm for vertex colouring, its application in scheduling exams, and the challenges related to achieving optimal colouring.

3.1.5 Example of Non-Optimal Colouring

This section discusses the concept of vertex colouring in graph theory, illustrating the process and significance of finding optimal and non-optimal colourings.

3.1.6 Upper Bound on Vertex Chromatic Number

This section introduces vertex coloring, focusing on its application in scheduling and defines the vertex chromatic number and its upper bound.

Edge Colouring

This section discusses edge colouring, its significance in real-world applications, and the concept of edge chromatic number.

3.2 Section Overview

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3.2.1 Motivation for Edge Colouring

This section discusses the application and theoretical significance of edge colouring in graph theory, particularly focusing on its relevance in real-world scenarios like scheduling tournaments.

3.2.2 Edge Chromatic Number

This section explores the concept of edge chromatic numbers, detailing the significance of edge coloring in graph theory and its challenges.

3.2.3 Lower and Upper Bound on Edge Chromatic Number

This section discusses the concepts of edge chromatic number, its lower and upper bounds, and the challenges associated with determining its value.

Conclusion

The conclusion summarizes key insights on vertex and edge colouring, emphasizing their chromatic numbers and the associated challenges.

3.3 Section Overview

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Learning Objectives

  • Vertex colouring ensures no two adjacent vertices in a graph share the same colour.

  • The vertex chromatic number is the minimum number of colours required for a proper vertex colouring.

  • The edge chromatic number is the minimum number of colours needed to colour the edges such that no two adjacent edges share the same colour.

Key Concepts

Vertex Colouring

A method of assigning colours to the vertices of a graph so that no two adjacent vertices have the same colour.

Vertex Chromatic Number (χ(G))

The minimum number of colours needed to colour the vertices of a graph without adjacent vertices sharing the same colour.

Edge Colouring

A method of assigning colours to the edges of a graph such that no two edges that share a vertex have the same colour.

Edge Chromatic Number (χ₀(G))

The minimum number of colours required to colour the edges of a graph without adjacent edges sharing the same colour.

Greedy Algorithm for Colouring

An approach to colouring where each vertex is coloured with the first available colour not assigned to its adjacent vertices.

Gupta-Vizing Theorem

A theorem establishing that the edge chromatic number of a simple graph is bounded by the maximum degree of that graph plus one.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

1 more question available

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