Why should you care?

Networks, grids, and dependencies become graph problems.

See it live — copy this example

Run snippets in a .NET console app, LINQPad, or https://dotnetfiddle.net. Write Big O above every solution.

var g = new Dictionary<int, List<int>>();
void AddEdge(int u, int v) {
  if (!g.ContainsKey(u)) g[u] = new();
  g[u].Add(v);
}
// Detect Cycle in Graph

What happened?

• Build adjacency first; then BFS/DFS/shortest path.
• Follow the steps below — typing the code yourself is the fastest way to learn.

Practice next

1. Type the snippet in a C# console or LINQPad.
2. Write Big O on top of your solution.
3. Test empty / single-element edge cases.
4. Add a failing test then fix it.
5. Rename variables to domain words.

Remember

You can code a small C# example for Detect Cycle in Graph. You know the complexity class. You tested at least one edge case.

Detect Cycle in Graph drill

AlgoVerse interview prompt on detect cycle in graph.

Outcome: You recognize the pattern and ship a correct C# sketch.