The Seven Bridges of Königsberg

Step 4: Dots and Lines

In 1736 Leonhard Euler proved no walk could cross Königsberg's seven bridges exactly once, and invented graph theory doing it. Try the puzzle yourself, then see Euler's trick.

1. A Sunday Puzzle
2. Try It Yourself
3. Euler Gets a Letter
4. Dots and Lines
5. The Rule
6. What It Started