Is the walk possible?
The solution is proposed by the Swiss mathematician Leonhard Euler. Let’s start, to solve the problem Leonhard Euler started with the assumption that the walk is possible. For one confrontation with a particular landmass, different than the initial or final one, two different bridges must be taken into consideration, one bridge for entry to the landmass and the other one for exiting it. Therefore, each landmass must be an endpoint of an amount of bridges equaling two times the number of how many times it is confronted over the walk. Consequently, each landmass, with the possibility of exception of the initial and final ones if they are different, must be an endpoint of an even amount of bridges. Now, for our example which is known as Bridges of Königsberg we have one landmass as an endpoint of five bridges and the others are endpoints of three bridges. Therefore, the walk is not possible.