Playground & Quiz

Free exploration sandbox and test your knowledge

Playground & Quiz: Master Your Knowledge

Welcome to the final module! You've journeyed through graph foundations, trees and properties, paths and coloring, network flow, spectral theory, and random networks. Now it's time to consolidate your knowledge through hands-on experimentation and comprehensive testing.

Use the interactive playground to build graphs and run algorithms. Then take the comprehensive quiz to test your understanding across all topics. Are you ready to become a graph theory expert?

What You'll Do

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Build Graphs
Create custom graphs with vertices and edges
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Run Algorithms
BFS, DFS, coloring, and connectivity
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Test Knowledge
Comprehensive quiz covering all topics

Interactive Graph Playground

Build your own graphs and explore algorithms! Click to add vertices, connect them with edges, and run various graph algorithms to see them in action.

Click anywhere to add a vertex
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Vertices
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Edges
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Density
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Avg Degree

Tips

  • Use preset graphs to explore famous graph structures
  • BFS/DFS start from the selected vertex (or first vertex if none selected)
  • Greedy coloring assigns colors to minimize conflicts
  • Try building your own graphs to test different algorithms!

Graph Theory Quiz

Test your knowledge! This comprehensive quiz covers all topics from foundations to advanced network theory. Choose your difficulty level and see how well you understand graphs.

Question 1 of 24Score: 0/0
Foundations
What is the degree of a vertex in a graph?
easy

Challenge Problems

Challenge 1: Prove Euler's Formula

Use induction on the number of edges to prove V - E + F = 2 for connected planar graphs. What happens when you remove an edge?

Hint: Consider two cases - does removing the edge disconnect the graph or remove a face?
Challenge 2: K₅ is Non-Planar

Prove that the complete graph K₅ cannot be drawn in the plane without edge crossings. Use Euler's formula and the edge-face inequality.

Hint: K₅ has 5 vertices and 10 edges. If planar, E ≤ 3V - 6. Does this hold?
Challenge 3: Chromatic Polynomial

Find the chromatic polynomial P(G, k) for a cycle C₄. How many ways can you color it with k colors? Verify that P(C₄, 2) = 2 (only 2 proper 2-colorings exist).

Hint: Use the deletion-contraction recurrence: P(G, k) = P(G-e, k) - P(G/e, k).
Challenge 4: Hamiltonian vs Eulerian

Construct a graph that is Eulerian but not Hamiltonian. Then construct one that is Hamiltonian but not Eulerian. Can a graph be both?

Hint: Think about degree conditions and cycle lengths.
Challenge 5: Spectral Gap

For the complete graph Kₙ, find all eigenvalues of the Laplacian matrix. Why is the spectral gap λ₂ = n maximal among all graphs on n vertices?

Hint: The Laplacian of Kₙ is L = nI - J where J is the all-ones matrix.

Further Exploration

Graph Isomorphism Problem

Determining whether two graphs are structurally identical. Famously solved in quasi-polynomial time by Babai (2015) but not known to be in P.

Graph Neural Networks

Machine learning on graph-structured data. Used in drug discovery, social network analysis, and recommendation systems.

Expander Graphs

Sparse graphs with strong connectivity properties. Applications in error-correcting codes, cryptography, and derandomization.

Algebraic Graph Theory

Using group theory to study graph symmetries. Cayley graphs connect group structure to graph properties.

Recommended Resources

Textbooks & References

  • Introduction to Graph Theory by Douglas West - Comprehensive
  • Graph Theory by Reinhard Diestel - Graduate level, free online
  • Algebraic Graph Theory by Chris Godsil - Spectral methods
  • Networks, Crowds, and Markets by Easley & Kleinberg - Applications

Online Resources

  • OEIS - Integer sequences related to graphs
  • NetworkX - Python library for network analysis
  • Gephi - Visualization software for large graphs
  • arXiv:math.CO - Latest research in combinatorics
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Congratulations!

You've completed the Graph Theory learning module! You now understand fundamental concepts, can analyze graph properties, implement algorithms, and have the foundation to explore advanced topics.

Mastered: Vertices, edges, degree, connectivity, trees, spanning trees

Explored: BFS, DFS, Dijkstra, Eulerian/Hamiltonian paths

Applied: Graph coloring, planarity testing, network flow

Advanced: Spectral theory, random graphs, scale-free networks

Practiced: Interactive building, algorithm visualization, comprehensive quiz

Share your achievement and continue exploring mathematics!