def dijkstra(aGraph, start):
pq = PriorityQueue()
start.setDistance(0)
pq.buildHeap([(v.getDistance(), v) for v in aGraph])
while not pq.isEmpty():
currentVert = pq.delMin()
for nextVert in currentVert.getConnections():
newDist = currentVert.getDistance() \
+ currentVert.getWeight(nextVert)
if newDist < nextVert.getDistance():
nextVert.setDistance(newDist)
nextVert.setPred(currentVert)
pq.decreaseKey(nextVert, newDist)
def dijkstra(G, start):
'''最短路径算法,时间复杂度:O((V+E)logV)
需要整个图，实际运用不现实
距离矢量路由算法只需要一部分图顶点'''
start = G.getVertex(start)
start.setDistance(0)
PriQueue = PriorityQueue() #加入队列
PriQueue.buildHeap([(v.getDistance(), v) for v in G])
while not PriQueue.isEmpty():
currVert = PriQueue.delMin()
for nbr in currVert.getConnections():
newDist = currVert.getDistance() + currVert.getWeight(nbr)
if newDist < nbr.getDistance():
nbr.setPred(currVert)
nbr.setDistance(newDist)
PriQueue.decreaseKey(nbr, newDist)
def prim(G, start):
'''贪婪算法系列算法,时间复杂度:O((V+E)logV + V)'''
for v in G:
v.setDistance(sys.maxsize)
v.setPred(None)
start = G.getVertex(start)
start.setDistance(0)
PriQueue = PriorityQueue() #创建优先队列
PriQueue.buildHeap([(v.getDistance(), v) for v in G])
while not PriQueue.isEmpty():
currVert = PriQueue.delMin()
for nbr in currVert.getConnections():
newDist = currVert.getDistance() + currVert.getWeight(nbr)
if nbr in PriQueue and newDist < nbr.getDistance():
nbr.setPred(currVert)
nbr.setDistance(newDist)
PriQueue.decreaseKey(nbr, newDist)
