为什么我的广度优先搜索算法如此之慢？

Question

我正在用Python实现广度优先搜索算法来解决8益智游戏http://mypuzzle.org/sliding。有人告诉我，这个算法运行时间不应超过几分钟，但它运行了一个多小时。我的算法或实现有问题吗？或者是那个告诉我这可能在几分钟内错误运行的人？

这是我的代码：

编辑：你可以在命令行中使用python driver.py bfs <nine numbers separated by commas>运行它我正在使用python driver.py bfs 9,3,7,5,0,6,4,1,2

driver.py

import sys
from SearchAlgorithms import bfs#, dfs, ast, ida

if __name__=='__main__':
    board = [int(s) for s in sys.argv[2].split(',')]
    if(sys.argv[1]=='bfs'):
        output = bfs(board)
    elif(sys.argv[1]=='dfs'):
        output = bfs(board)
    elif(sys.argv[1]=='ast'):
        output = bfs(board)
    elif(sys.argv[1]=='ida'):
        output = bfs(board)
    else:
        raise IOError
    print(output)

SearchAlgorithms.py

from queue import Queue
import math
import time
import copy

class Board:
    def __init__(self, data, path=[]):
        self.data = data
        self.path = path
    def neighbors(self):
        neighbors = []
        board_width = int(math.sqrt(len(self.data)))
        if self.data.index(0) - board_width >= 0:
            new_data = copy.deepcopy(self.data)
            new_data[self.data.index(0)], new_data[self.data.index(0) - board_width] = self.data[self.data.index(0) - board_width], 0
            neighbors.append(Board(new_data, self.path + ['Up']))
        if self.data.index(0) + board_width < len(self.data):
            new_data = copy.deepcopy(self.data)
            new_data[self.data.index(0)], new_data[self.data.index(0) + board_width] = self.data[self.data.index(0) + board_width], 0
            neighbors.append(Board(new_data, self.path + ['Down']))  
        if self.data.index(0) - 1 >= 0:
            new_data = copy.deepcopy(self.data)
            new_data[self.data.index(0)], new_data[self.data.index(0) - 1] = self.data[self.data.index(0) - 1], 0
            neighbors.append(Board(new_data, self.path + ['Left']))
        if self.data.index(0) + 1 < len(self.data):
            new_data = copy.deepcopy(self.data)
            new_data[self.data.index(0)], new_data[self.data.index(0) + 1] = self.data[self.data.index(0) + 1], 0
            neighbors.append(Board(new_data, self.path + ['Right']))
        return neighbors

def bfs(board):
    before = time.time()
    goal = sorted(board)
    graph = Board(board)
    frontier = [graph]
    explored = set()
    count = 0
    while frontier:
        count +=1
        if count % 100 == 0:
            print(count)
        state = frontier.pop(0)
        explored.add(state)

        if state.data == goal:
            return {'path_to_goal': reversed(state.path),
                    'cost_of_path': len(state.path),
                    'nodes_expanded': len(explored),
                    'fringe_size': len(frontier),
                    'running_time': time.time() - before
                                             }
        for neighbor in state.neighbors():
            if neighbor not in set().union(frontier, explored) :
                frontier.append(neighbor)
    return False 

感谢您的帮助！