The Seven Bridges

Where graph theory began

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A graph is a set of vertices (dots) joined by edges (lines). Only the connections matter.
• An Euler path (every edge exactly once) needs 0 or 2 odd-degree vertices.
• Start and end at the odd vertices, if there are any.

Steps

1. A Sunday stroll
2. Dots and lines
3. Draw the house
4. Back where you started
5. The street sweeper
6. Fix Königsberg