def addMatch(v, w):
            '''Here with an S-S edge vw connecting vertices in different structure trees.
Find the corresponding augmenting path and use it to augment the matching.'''
            alternate(v)
            alternate(w)
            matching[v] = w
            matching[w] = v
Here with an S-S edge vw connecting vertices in different structure trees.
Find the corresponding augmenting path and use it to augment the matching.
recipes/Python/221251_Maximum_cardinality_matching_general/recipe-221251.py