algoritmo de implementación dijkstra ejemplo de código de Python

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Ejemplo: Python del algoritmo de dijkstra

import sys


classVertex:def__init__(self,node):self.id=nodeself.adjacent=#Set distance to infinity for all nodes
        self.distance = sys.maxsize
        #Mark all nodes unvisited
        self.visited = False
        #Predecessor
        self.previous = None

    def __lt__(self, other):return self.distance < other.distance

    def add_neighbor(self, neighbor, weight=0):
        self.adjacent[neighbor]= weight

    def get_connections(self):return self.adjacent.keys()

    def get_id(self):return self.id

    def get_weight(self, neighbor):return self.adjacent[neighbor]

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

    def get_distance(self):return self.distance

    def set_previous(self, prev):
        self.previous = prev

    def set_visited(self):
        self.visited = True

    def __str__(self):returnstr(self.id)+' adjacent: '+str([x.id for x in self.adjacent])classGraph:def__init__(self):self.vert_dict=
        self.num_vertices =0

    def __iter__(self):returniter(self.vert_dict.values())

    def add_vertex(self, node):
        self.num_vertices = self.num_vertices +1
        new_vertex =Vertex(node)
        self.vert_dict[node]= new_vertex
        return new_vertex

    def get_vertex(self, n):if n in self.vert_dict:return self.vert_dict[n]else:return None

    def add_edge(self, frm, to, cost=0):if frm not in self.vert_dict:
            self.add_vertex(frm)if to not in self.vert_dict:
            self.add_vertex(to)

        self.vert_dict[frm].add_neighbor(self.vert_dict[to], cost)
        self.vert_dict[to].add_neighbor(self.vert_dict[frm], cost)

    def get_vertices(self):return self.vert_dict.keys()

    def set_previous(self, current):
        self.previous = current

    def get_previous(self, current):return self.previous


def shortest(v, path):''' make shortest path from v.previous'''if v.previous:
        path.append(v.previous.get_id())shortest(v.previous, path)return


import heapq


def dijkstra(aGraph, start, target):print('''Dijkstra's shortest path''')#Set the distance for the start node to zero
    start.set_distance(0)#Put tuple pair into the priority queue
    unvisited_queue =[(v.get_distance(), v)for v in aGraph]
    heapq.heapify(unvisited_queue)whilelen(unvisited_queue):#Pops a vertex with the smallest distance
        uv = heapq.heappop(unvisited_queue)
        current = uv[1]
        current.set_visited()#fornext in v.adjacent:for next in current.adjacent:#ifvisited, skipif next.visited:continue
            new_dist = current.get_distance()+ current.get_weight(next)if new_dist < next.get_distance():
                next.set_distance(new_dist)
                next.set_previous(current)print('updated : current = %s next = %s new_dist = %s' 
                      %(current.get_id(), next.get_id(), next.get_distance()))else:print('not updated : current = %s next = %s new_dist = %s' 
                      %(current.get_id(), next.get_id(), next.get_distance()))#Rebuild heap
        # 1. Pop every item
        whilelen(unvisited_queue):
            heapq.heappop(unvisited_queue)
        # 2. Put all vertices not visited into the queue
        unvisited_queue =[(v.get_distance(), v)for v in aGraph ifnot v.visited]
        heapq.heapify(unvisited_queue)if __name__ =='__main__':

    g =Graph()

    g.add_vertex('a')
    g.add_vertex('b')
    g.add_vertex('c')
    g.add_vertex('d')
    g.add_vertex('e')
    g.add_vertex('f')

    g.add_edge('a','b',7)
    g.add_edge('a','c',9)
    g.add_edge('a','f',14)
    g.add_edge('b','c',10)
    g.add_edge('b','d',15)
    g.add_edge('c','d',11)
    g.add_edge('c','f',2)
    g.add_edge('d','e',6)
    g.add_edge('e','f',9)print('Graph data:')for v in g:for w in v.get_connections():
            vid = v.get_id()
            wid = w.get_id()print('( %s , %s, %3d)'%(vid, wid, v.get_weight(w)))dijkstra(g, g.get_vertex('a'), g.get_vertex('e'))

    target = g.get_vertex('e')
    path =[target.get_id()]shortest(target, path)print('The shortest path : %s'%(path[::-1]))

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