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from collections import defaultdict
class Graph(object):
def __init__(self):
self.nodes = set()
self.edges = defaultdict(list)
self.distance = {}
def add_node(self, node):
self.nodes.add(node)
def add_edge(self, from_node, to_node, distance):
self.edges[from_node].append(to_node)
self.distance[(from_node, to_node)] = distance
def dijkstra(graph, init):
visited = {init: 0}
path = defaultdict(list)
nodes = set(graph.nodes)
print("Nodes: %s" % nodes)
while nodes:
min_node = None
for node in nodes:
if node in visited:
if min_node is None:
min_node = node
elif visited[node] < visited[min_node]:
min_node = node
if min_node is None:
break
nodes.remove(min_node)
current_weight = visited[min_node]
for edge_node in graph.edges[min_node]:
weight = current_weight + graph.distance[(min_node, edge_node)]
if edge_node not in visited or weight < visited[edge_node]:
visited[edge_node] = weight
path[edge_node] = min_node
return visited
if __name__ == "__main__":
g = Graph()
g.add_node('A')
g.add_node('B')
g.add_node('C')
g.add_node('D')
g.add_node('E')
g.add_node('F')
g.add_node('G')
g.add_edge('A', 'B', 12)
g.add_edge('A', 'C', 7)
g.add_edge('B', 'D', 1)
g.add_edge('B', 'A', 12)
g.add_edge('D', 'E', 8)
g.add_edge('C', 'F', 3)
g.add_edge('D', 'G', 5)
g.add_edge('F', 'B', 1)
g.add_edge('F', 'G', 2)
g.add_edge('C', 'D', 13)
g.add_edge('E', 'B', 6)
print(f"Initial Distance: { g.distance }")
print(f"Visited: { dijkstra(g, 'A') }")