k,e] is directed from an even vertex to an odd vertex and each arc of [[?
In [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], the odd vertices and even vertices alternate and an odd vertex is obtained by adding aj to its preceding (even) vertex, along the anti-directed cycle, and an even vertex is obtained from its preceding (odd) vertex by adding (-bj) to it.
Based on the optimal path search, a trace (single stroke) is assessed in the graph until an odd vertex
In figure 2, for example, A is an odd vertex
because three curves go to it.
e] ([beta], [delta]) by orienting each of its edges from its even to its odd vertex
one obtains edges oriented in the directions up, down, left or right.