The Königsberg Bridge Problem and the Friendship Theorem

Wenda Li 🌐

July 19, 2013

This is a development version of this entry. It might change over time and is not stable. Please refer to release versions for citations.


This development provides a formalization of undirected graphs and simple graphs, which are based on Benedikt Nordhoff and Peter Lammich's simple formalization of labelled directed graphs in the archive. Then, with our formalization of graphs, we show both necessary and sufficient conditions for Eulerian trails and circuits as well as the fact that the Königsberg Bridge Problem does not have a solution. In addition, we show the Friendship Theorem in simple graphs.


BSD License


Session Koenigsberg_Friendship