python实现八皇后问题

 1 import random
 2 
 3 def judge(state, nextX):   #判断是否和之前的皇后状态有冲突
 4     nextY = len(state)
 5     for i in range(nextY):
 6         if abs(state[i]-nextX) in (0,nextY-i):
 7             return True
 8     return False
 9 
10 def queens(num = 8, state = ()):
11     for pos in range(num):
12         if not judge(state, pos):
13             if len(state) == num-1:
14                 yield (pos,)   #(pos,)中的逗号使其必须被设置为元组而不是简单地加上括号
15             else:
16                 for result in queens(num, state+(pos,)):
17                     yield (pos,)+result
18 
19 def randomPrint(solution):
20     for i in range(8):
21         print( '•'*solution[i]+'X'+'•'*(8-solution[i]-1))
22 
23 ans = int(len(list(queens(8))))
24 print(ans)
25 randomPrint(random.choice(list(queens())))  #随机输出一种情况