from pythonds.basic import Queue class Vertex: def __init__(self,key): self.id = key self.connectedTo = {} def addNeighbor(self,nbr,weight=0): self.connectedTo[nbr] = weight def __str__(self): return str(self.id) + ' connectedTo: ' + str([x.id for x in self.connectedTo]) def getConnections(self): return self.connectedTo.keys() def getId(self): return self.id def getWeight(self,nbr): return self.connectedTo[nbr] class Graph: def __init__(self): self.vertList = {} self.numVertices = 0 def addVertex(self,key): self.numVertices = self.numVertices + 1 newVertex = Vertex(key) self.vertList[key] = newVertex return newVertex def getVertex(self,n): if n in self.vertList: return self.vertList[n] else: return None def __contains__(self,n): return n in self.vertList def addEdge(self,f,t,cost=0): if f not in self.vertList: nv = self.addVertex(f) if t not in self.vertList: nv = self.addVertex(t) self.vertList[f].addNeighbor(self.vertList[t], cost) def getVertices(self): return self.vertList.keys() def __iter__(self): return iter(self.vertList.values()) def bfs(g,start): start.setDistance(0) start.setPred(None) vertQueue=Queue() vertQueue.enqueue(start) while (vertQueue.size()>0): currentVert=vertQueue.dequeue() for nbr in currentVert.getConnections(): if (nbr.getColor()=='White'): nbr.setColor('gray') nbr.setDistance(currentVert.getDistance()+1) nbr.setPred(currentVert) vertQueue.enqueue(nbr) currentVert.setColor('black') List=["""1:A,2:B,3:C,4:D,5:E,6:F"""] g=Graph() for i in range(6): g.addVertex(i) g.addEdge(1,2,7) g.addEdge(2,1,2) g.addEdge(1,3,5) g.addEdge(1,6,1) g.addEdge(2,4,7) g.addEdge(2,5,3) g.addEdge(3,2,2) g.addEdge(3,6,8) g.addEdge(4,1,1) g.addEdge(4,5,2) g.addEdge(4,6,4) g.addEdge(5,1,6) g.addEdge(5,4,5) g.addEdge(6,2,1) g.addEdge(6,5,8) bfs(g,)优化这段代码

首先，这段代码中的bfs函数调用需要传入两个参数，一个是图g，一个是起始顶点start。因此，需要在函数调用时传入起始顶点参数。

其次，在bfs函数中，setDistance、setColor、setPred等方法的实现是未知的，需要在Vertex类中进行实现。为了实现bfs算法，需要在Vertex类中添加以下代码：

def setColor(self, color):
    self.color = color

def getColor(self):
    return self.color

def setDistance(self, dist):
    self.distance = dist

def getDistance(self):
    return self.distance

def setPred(self, pred):
    self.pred = pred

def getPred(self):
    return self.pred

最后，在bfs函数中，需要将起始顶点的颜色设置为灰色，将距离设置为0，将前驱顶点设置为None。因此，可以在函数开头添加以下代码：

start.setColor('gray')
start.setDistance(0)
start.setPred(None)

优化后的bfs函数代码如下：

def bfs(g, start):
    start.setColor('gray')
    start.setDistance(0)
    start.setPred(None)
    vertQueue = Queue()
    vertQueue.enqueue(start)
    while (vertQueue.size() > 0):
        currentVert = vertQueue.dequeue()
        for nbr in currentVert.getConnections():
            if (nbr.getColor() == 'White'):
                nbr.setColor('gray')
                nbr.setDistance(currentVert.getDistance() + 1)
                nbr.setPred(currentVert)
                vertQueue.enqueue(nbr)
        currentVert.setColor('black')