K\"onigsberg's bridges problem

K\"{o}nigsberg's bridges problem --- задача о кенигсбергских мостах.

In 1736 Euler solved a recreational puzzle interesting to the inhabitants of K\"{o}nigsberg (now Kaliningrad). Kaliningrad sits across the river Pregel with seven bridges connecting the various banks and islands of the river as shown. The problem is whether or not it is possible to follow a circular walk starting and finishing at the same river bank and crossing each bridge precisely once.

See also

• Eulerian graph.