# sp.appendleft(pred[curr])
# curr = pred[curr]
# else:
# print(f'No path to {v}')
# break # cycles are ignored
# else:
# sp.appendleft(source)
# all_sp.append(list(sp))
#
# return all_sp
if __name__ == '__main__':
dg = Digraph() # clrs example
dg.add_weighted_edges_from([('t', 'x', 5), ('t', 'y', 8), ('t', 'z', -4), ('x', 't', -2),
('y', 'x', -3), ('y', 'z', 9), ('z', 'x', 7), ('z', 's', 2),
('s', 't', 6), ('s', 'y', 7)])
print(f'Graph: {dg}')
print(f'Weights: {dg.weights}')
print(bellman_ford(dg, 's'))
print('')
# dg = Digraph()
# dg.add_edge('s', 'a', 3) # cormen book example
# dg.add_edge('s', 'c', 5)
# dg.add_edge('s', 'e', 2)
# dg.add_edge('a', 'b', -4)
# dg.add_edge('b', 'g', 4)
# dg.add_edge('c', 'd', 6)
# dg.add_edge('d', 'c', -3)
# dg.add_edge('d', 'g', 8)
for v in g.neighbors(u):
d = dist[u] + g.weight(u, v)
if d < dist[v]: # relaxation
dist[v] = d
pred[v] = u
heappush(minq,
(dist[v], v)) # could have duplicate vertices in minq
return pred, dist
# to get the path, refer to the predecessors dictionary
if __name__ == '__main__':
dg = Digraph() # clrs example
dg.add_weighted_edges_from([('s', 't', 10), ('s', 'y', 5), ('t', 'x', 1),
('t', 'y', 2), ('x', 'z', 4), ('y', 't', 3),
('y', 'x', 9), ('y', 'z', 2), ('z', 's', 7),
('z', 'x', 6)])
print(dg)
print(dijkstra(dg, 's'))
print('-----')
dg = Digraph() # graph theory example youtube
dg.add_weighted_edges_from([(0, 1, 4), (0, 2, 1), (1, 3, 1), (2, 1, 2),
(2, 3, 5), (3, 4, 3)])
print(dg)
print(dijkstra(dg, 0))
print('-----')
# cp3 4.17 in https://visualgo.net/en/sssp
dg = Digraph()
dg.add_weighted_edges_from([(0, 1, 2), (0, 2, 6), (0, 3, 7), (1, 3, 3),
# dist[v] = sys.maxsize
# pred[v] = None
# dist[source] = 0
#
# for v1 in sortedv:
# for v2 in g.neighbors(v1):
# if dist[v1] + g.weight(v1, v2) < dist[v2]: # relaxation
# dist[v2] = dist[v1] + g.weight(v1, v2)
# pred[v2] = v1
#
# for v in g.vertices(): # generate all shortest paths
# if v == source or pred[v] is None:
# continue
# sp = deque(v) # shortest path
# curr = v
# while pred[curr] != source:
# sp.appendleft(pred[curr])
# curr = pred[curr]
# sp.appendleft(source)
# all_sp.append(list(sp))
#
# return all_sp
if __name__ == '__main__':
dg = Digraph() # clrs example
dg.add_weighted_edges_from([('r', 's', 5), ('r', 't', 3), ('s', 't', 2),
('s', 'x', 6), ('t', 'x', 7), ('t', 'y', 4),
('t', 'z', 2), ('x', 'y', -1), ('x', 'z', 1),
('y', 'z', -2)])
print(dag_sssp(dg, 's'))