In Konigsberg, Germany, a river ran through the city such that in its center was an island, and after passing the island, the river broke into two parts. Seven bridges were built so that the people of the city could get from one part to another. A crude map of the center of Konigsberg might look like this:
The people wondered whether or not one could walk around the city in a way that would involve crossing each bridge exactly once.© BrainMass Inc. brainmass.com September 21, 2018, 2:42 am ad1c9bdddf - https://brainmass.com/math/analytic-geometry/euler-path-problem-the-seven-bridges-of-konigsberg-32451
In the graph, the vertex1 represents the island, which is connected to the lands by 5 bridges, vertices 2, 3 and 4 represent the lands. This graph has 7 edges, which represent the 7 bridges.
Our goal is now into trying to find a path which goes through all 7 edges ...
A euler path problem is solved. The solution is detailed and well presented.