Day 23 — Topological Sort
This chapter is being written. Check back soon!
What you’ll learn here
- What it means for a graph to be a DAG (Directed Acyclic Graph)
- Kahn’s algorithm — repeatedly take a node with indegree 0, BFS-style
- DFS post-order — recursive variant that’s a one-liner once DFS is set up
- Real-world applications: build systems (make, npm), task scheduling, course prerequisites, spreadsheet recalculation
If there’s any ordering at all on your dependencies, topological sort is the algorithm that finds it — and refuses to lie when one doesn’t exist (cycle detection).