def __init__(self, nodes):

self.nodes = nodes

# find node by name (static method)

@staticmethod

def findByNameStatic(nodes, name):

return next((node for node in nodes if node.name==name), None)

# filter function based on max distance

@staticmethod

def distanceLessThanFilter(route, distance):

return route.getDistance() < distance

# find node by name

def findByName(self, name):

return next((node for node in self.nodes if node.name==name), None)

# generate a route based on string input, 'A->B->C' for example.

def getRouteFromString(self, routeString):

nodes = [self.findByName(n) for n in routeString.split('-')]

return self.getRouteBasedOnNodes(nodes)

# generate a route based on provided nodes (in sequence).

# return None when nodes are not connected.

def getRouteBasedOnNodes(self, nodes):

if len(nodes) <= 1:

return 0

else:

link = nodes[0].findLinkByChildNode(nodes[1].name)

if link is None:

return None

else:

nodes.pop(0)

distance = self.getRouteBasedOnNodes(nodes)

return link.weight + distance if distance is not None else None

# find shortest distance between two nodes.

# return None when not connected.

def getShortestDistanceBetweenTwoNodes(self, startName, endName):

startNode = self.findByName(startName)

endNode = self.findByName(endName)

if startNode is None or endNode is None:

return None

else:

return self.findShortestRoute(startNode, endName)

def findShortestRoute(self, startNode, destinationName):

# get routes to process by getting all out going links of the starting node

candidateRoutes = Routes([Route([link]) for link in startNode.getLinks()])

minRoute = None

# candiate routes are the routes to process.

# they can be empty when no more routes can have distances less than the current minimum distance

# or cannot find any more routes

while candidateRoutes.len() > 0:

# finished routes store the routes connecting start node and end node

finishedRoutes = candidateRoutes.getRoutesEndedWithNode(destinationName)

_minRoute = finishedRoutes.getMinDistance()

minRoute = _minRoute if minRoute is None or (_minRoute is not None and minRoute.getDistance() > _minRoute.getDistance()) else minRoute

# filter out routes having bigger distance than min route

candidateRoutes = Routes([route for route in candidateRoutes.getRoutes() if minRoute is None or route.getDistance() < minRoute.getDistance()])

# all candidate routes go one step further. Store the new generated routes

candidateRoutes = Routes([Route([]).copyFrom(route).addNextLink(link) \

for route in candidateRoutes.getRoutes() for link in self.findByName(route.getLastLink().child).getLinks() \

if not route.hasNode(link.child) or (link.child == destinationName and startNode.name == destinationName)])

return minRoute

# find trips between two nodes with the constraint of max round of interation.

# return None when not found.

def findTripsBetweenWithMaxRound(self, startName, endName, maxRound):

startNode = self.findByName(startName)

endNode = self.findByName(endName)

if startNode is None or endNode is None:

return None

else:

return self.findRoutesWithMaxRound(startNode, endName, maxRound)

def findRoutesWithMaxRound(self, startNode, destinationName, maxRound):

# get routes to process by getting all out going links of the starting node

candidateRoutes = Routes([Route([link]) for link in startNode.getLinks()])

count = 0

finishedRoutes = None

while candidateRoutes.len() > 0 and maxRound is not None and count < maxRound:

# finished routes store the routes connecting start node and end node

finishedRoutes = candidateRoutes.getRoutesEndedWithNode(destinationName).merge(finishedRoutes)

# all candidate routes go one step further. Store the new generated routes

candidateRoutes = Routes([Route([]).copyFrom(route).addNextLink(link) \

for route in candidateRoutes.getRoutes() for link in self.findByName(route.getLastLink().child).getLinks()])

count = count + 1

return finishedRoutes

# find trips between two nodes with the constraint of exact round of interation.

# return None when not found.

def findTripsBetweenWithExactRound(self, startName, endName, round):

startNode = self.findByName(startName)

endNode = self.findByName(endName)

if startNode is None or endNode is None:

return None

else:

return self.findRoutesWithExactRound(startNode, endName, round)

def findRoutesWithExactRound(self, startNode, destinationName, round):

# get routes to process by getting all out going links of the starting node

candidateRoutes = Routes([Route([link]) for link in startNode.getLinks()])

count = 0

finishedRoutes = None

while candidateRoutes.len() > 0 and round is not None and count < round:

if count + 1 == round:

# finished routes store the routes connecting start node and end node

finishedRoutes = candidateRoutes.getRoutesEndedWithNode(destinationName).merge(finishedRoutes)

# all candidate routes go one step further. Store the new generated routes

candidateRoutes = Routes([Route([]).copyFrom(route).addNextLink(link) \

for route in candidateRoutes.getRoutes() for link in self.findByName(route.getLastLink().child).getLinks()])

count = count + 1

return finishedRoutes

# find trips between two nodes with the constraint of max distance.

# return None when not found.

def findTripsBetweenWithMaxDistance(self, startName, endName, distance):

startNode = self.findByName(startName)

endNode = self.findByName(endName)

if startNode is None or endNode is None:

return None

else:

return self.findRoutesWithMaxDistance(startNode, endName, distance)

def findRoutesWithMaxDistance(self, startNode, destinationName, distance):

# get routes to process by getting all out going links of the starting node

candidateRoutes = Routes([Route([link]) for link in startNode.getLinks()])

finishedRoutes = None

# define filter function with partial function

lessThanFilterFunc = partial(Dag.distanceLessThanFilter, distance=distance)

while candidateRoutes.len() > 0:

# finished routes store the routes connecting start node and end node

finishedRoutes = candidateRoutes.getRoutesEndedWithNode(destinationName).filter(lessThanFilterFunc).merge(finishedRoutes)

# all candidate routes go one step further. Store the new generated routes

candidateRoutes = Routes([Route([]).copyFrom(route).addNextLink(link) \

for route in candidateRoutes.getRoutes() for link in self.findByName(route.getLastLink().child).getLinks()])

# filter out routes having more distance than the max distance

candidateRoutes = Routes([route for route in candidateRoutes.getRoutes() if route.getDistance() < distance])