Seven Bridges of Königsberg

Classic problem in graph theory

The Seven Bridges of Königsberg is a historical puzzle asking for a walking tour through the bridges of the city of Königsberg (now Kaliningrad) where each of the city's bridges is crossed exactly once. Its mathematical formalization and proof of impossibility by Leonhard Euler, in 1736, laid the foundations of graph theory and foreshadowed the idea of topology.

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