The city of Königsberg, Germany was set on both sides of the Pregel River. As shown in a sketch map of the city (Figure 2.1(a)), seven bridges across the river connected two large islands and the mainland to one another. The people of Königsberg wondered whether or not one could walk around the city in a way that would involve crossing each bridge exactly once. Euler approached this problem by collapsing areas of land separated by the river into points (Figure 2.1(b)), and representing bridges as curves (Figure 2.1(c)).
KeywordsGeographic Information System Transportation Network Network Effect Network Externality Preferential Attachment
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