ABSTRACT
It is reasonable to say that graph theory was founded by the Swiss mathematician and physicist Leonhard Euler (see Appendix C). As we mentioned in Section 1.1.1, Euler addressed the St. Petersburg Academy in 1735 on the problem of the Königsberg bridges. The Prussian city of Königsberg was set on both sides of the Pregel River. It included a large island called The Kneiphof, and the river branched to the east of it. So there were four main land masses—we shall call them the four parts of the city, and label them A, B, C, D—connected to each other by seven bridges. For convenience we repeat our rough map of the city, on the left in Figure 11.1: The original Königsberg bridges. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315366890/f4bfe916-bec8-4e54-8a5a-ffef17c80cb7/content/fig11_1.tif"/>
