def al_acyclic_graph_3(): return Al([ Vx(0, (2, 3)), Vx(1, 2), Vx(2, (3, 4)), Vx(3, (5, 6)), Vx(4, 7), Vx(5, 7), Vx(6), Vx(7) ])
def al_cyclic_graph_1(): return Al([ Vx(0, (2, 3)), Vx(1, 2), Vx(2, (3, 4)), Vx(3, (5, 6)), Vx(4, 7), Vx(5, 7), Vx(6, 8), Vx(7), Vx(8, 2) ])
def al_acyclic_graph_1(): return Al([ Vx(0, (1, 2)), Vx(1, (4, 5)), Vx(2, (6, 7)), Vx(3, 7), Vx(4), Vx(5, 8), Vx(6, 8), Vx(7), Vx(8) ])
def al_acyclic_graph_2(): return Al([ Vx(0, (1, 2)), Vx(1, (4, 5)), Vx(2, (6, 7, 9)), Vx(3, 7), Vx(4), Vx(5, 8), Vx(6, 8), Vx(7, 9), Vx(8, 9), Vx(9), Vx(10, 2) ])
def al_acyclic_graph_4(): return Al([ Vx(0, (1, 2, 5)), Vx(1, (3, 4, 5)), Vx(2, 6), Vx(3, 7), Vx(4, 7), Vx(5, 8), Vx(6, 8), Vx(7, 9), Vx(8, 9), Vx(9), Vx(10, 12), Vx(11, 12), Vx(12, (6, 13)), Vx(13) ])
def al_acyclic_graph_5(): return Al([ Vx(0, 4), Vx(1, 5), Vx(2, (6, 7)), Vx(3, 7), Vx(4, 11), Vx(5, 11), Vx(6, 11), Vx(7, 8), Vx(8, (9, 10)), Vx(9), Vx(10), Vx(11, (12, 13, 14)), Vx(12), Vx(13), Vx(14) ])
def al_cyclic_graph_2(): return Al([Vx(0, (1, 2, 3)), Vx(1, 4), Vx(2, 4), Vx(3, 2), Vx(4, 3)])