A connected graph G is called an Euler graph, if there is a closed trail which includes every edge of the graph G.
All vertices of G are of even degree, and a connected graph G is Eulerian if and only if its edge set can be decomposed into cycles.
Examples of Euler Graph
Euler Circuit: A B C A
Euler Line: Ae1Be2Ce3
Euler Circuit: B C D E B D A B
Euler Line: Be2Ce3De4Ee7Be6De5Ae1
Euler Circuit: A B C D E F G H A E H D A
Euler Line: Ae2Be3Ce4De4Ee6Fe7G
e8He1Ae10Ee11He9De12
Euler Circuit: A B C D E C F A
Euler Line: Ae1Be2Ce3De4Ee5Ce6Fe7
Euler Circuit: A D B A C D A
Euler Line: Ae1Be2De5Ce4Ae3D
