class Dijkstra(object):
def __init__(self):
self.infinity = 1000000
self.shortestPathTo = {}
self.edgeTo = {}
self.minQueue = MinPriorityQueue()
def __initSingleSource(self, graph, startNode):
self.shortestPathTo = dict.fromkeys(graph, self.infinity)
self.edgeTo = dict.fromkeys(graph, None)
self.shortestPathTo[startNode] = 0
def findShortestPaths(self, graph, startNode):
self.__initSingleSource(graph, startNode)
self.minQueue.insert((self.shortestPathTo[startNode], startNode))
while not self.minQueue.empty():
dist, node = self.minQueue.extractMin()
self.__relaxation(graph, node)
return self.shortestPathTo, self.edgeTo
def __relaxation(self, graph, node):
for adjacentNode in graph[node]:
edgeDistance = graph[node][adjacentNode]
overallDistance = self.shortestPathTo[node] + edgeDistance
if self.shortestPathTo[adjacentNode] > overallDistance:
self.shortestPathTo[adjacentNode] = overallDistance
self.edgeTo[adjacentNode] = node
if self.minQueue.contains(adjacentNode):
self.minQueue.decreaseKey(self.shortestPathTo[adjacentNode], adjacentNode)
else:
self.minQueue.insert((self.shortestPathTo[adjacentNode], adjacentNode))
def __init__(self):
self.infinity = 1000000
self.shortestPathTo = {}
self.edgeTo = {}
self.minQueue = MinPriorityQueue()
