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Dijkstra.py
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Dijkstra.py
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from collections import defaultdict
class Graph:
def __init__(self):
self.nodes = set()
self.edges = defaultdict(list)
self.distances = {}
def addNode(self,value):
self.nodes.add(value)
def addEdge(self, fromNode, toNode, distance):
self.edges[fromNode].append(toNode)
self.distances[(fromNode, toNode)] = distance
#Implementing Dijkstra's Algorithm
def dijkstra(graph, initial):
visited = {initial : 0}
path = defaultdict(list)
nodes = set(graph.nodes)
while nodes:
minNode = None
for node in nodes:
if node in visited:
if minNode is None:
minNode = node
elif visited[node] < visited[minNode]:
minNode = node
if minNode is None:
break
nodes.remove(minNode)
currentWeight = visited[minNode]
for edge in graph.edges[minNode]:
weight = currentWeight + graph.distances[(minNode, edge)]
if edge not in visited or weight < visited[edge]:
visited[edge] = weight
path[edge].append(minNode)
return visited, path
graph1 = Graph()
graph1.addNode("A")
graph1.addNode("B")
graph1.addNode("C")
graph1.addNode("D")
graph1.addNode("E")
graph1.addNode("F")
graph1.addNode("G")
graph1.addEdge("A", "B", 2)
graph1.addEdge("A", "C", 5)
graph1.addEdge("B", "C", 6)
graph1.addEdge("B", "D", 1)
graph1.addEdge("B", "E", 3)
graph1.addEdge("C", "F", 8)
graph1.addEdge("D", "E", 4)
graph1.addEdge("E", "G", 9)
graph1.addEdge("F", "G", 7)
print(dijkstra(graph1, "A"))