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# 5.2: Euler Circuits and Walks

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The first problem in graph theory dates to 1735, and is called the Seven Bridges of Königsberg. In Königsberg were two islands, connected to each other and the mainland by seven bridges, as shown in figure 5.2.1. The question, which made its way to Euler, was whether it was possible to take a walk and cross over each bridge exactly once; Euler showed that it is not possible.