>>> import networkx as nx

>>> lrius = [ ['Jari', 'Amazones'], ['Xingú', 'Amazones'], ['Iriri', 'Xingú'],
...  ['Paru', 'Amazones'], ['Tapajós', 'Amazones'], ['Teles Pires', 'Tapajós'],
...  ['Juruena', 'Tapajós'], ['Arinos', 'Juruena'], 
...  ['Guaviare', 'Orinoco'], ['Inírida', 'Guaviare'], ['Arauca', 'Orinoco'] ]
>>> gr = nx.DiGraph()
>>> gr.add_edges_from(lrius)

--fi-creacio

>>> from rius import confluencia

--ini-enunciat

>>> confluencia(gr, 'Jari', 'Amazones')
1
>>> confluencia(gr, 'Iriri', 'Amazones')
2
>>> confluencia(gr, 'Amazones', 'Tapajós')
0
>>> confluencia(gr, 'Tapajós', 'Arinos')
0
>>> confluencia(gr, 'Xingú', 'Paru')
0

--fi-enunciat