You've learned Euler paths and circuits.
core concepts:
- Euler path visits every edge exactly once
- Euler circuit is an Euler path returning to start
- Undirected: or odd-degree vertices
- Directed: in-degree out-degree (with for endpoints)
Algorithm: Hierholzer's algorithm finds Euler paths in time.
Applications:
- Mail delivery and routing
- De Bruijn sequences
- DNA sequencing
When you see: "visit every edge exactly once" → Euler path. Check degree conditions first, then run Hierholzer.