The Seven Bridges of Koenigsberg is a notable historical problem in
mathematics. Its negative resolution by Leonhard Euler in 1735 laid
the foundations of graph theory and presaged the idea of topology.
The city of Koenigsberg in Prussia (now Kaliningrad, Russia) was set on
both sides of the Pregel River, and included two large islands which
were connected to each other and the mainland by seven bridges
The problem was to find a walk through the city that would cross each
bridge once and only once. The islands could not be reached by any route
other than the bridges, and every bridge must have been crossed
completely every time (one could not walk half way onto the bridge and
then turn around and later cross the other half from the other side).
Euler proved that the problem has no solution.
Usage
Koenigsberg
Format
An undirected igraph graph object with vertex attributes
‘name’ and ‘Euler_letter’, the latter is the notation
from Eulers original paper; and edge attributes name (the name
of the bridge) and ‘Euler_letter’, again, Euler's notation
from his paper.