graph={
    '5':['3','7'],
    '3':['2','4'],
    '7':['8'],
    '2':[],
    '4':['8'],
    '8':[],
}

visited=[] #list for visited nodes
queue=[] #initialize a queue

def bfs(visited, graph, node): #function for bfs
   visited.append(node)
   queue.append(node)

   while queue:
    m=queue.pop(0)
    print(m,end=' ')
    
    for neighbour in graph[m]:
      if neighbour not in visited:
        visited.append(neighbour)
        queue.append(neighbour)

#driver code
print("following is the breadth-first serach")
bfs(visited, graph, '5') #function calling