Python基于生成器迭代如何實(shí)現(xiàn)八皇后問題

小編給大家分享一下Python基于生成器迭代如何實(shí)現(xiàn)八皇后問題，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！

問題：有一個(gè)棋盤和8個(gè)要放到上面的皇后，唯一的要求是皇后之間不能形成威脅。也就是說，必須把他們防止成每個(gè)皇后都不能吃掉其他皇后的狀態(tài)。

# -*- coding: utf-8 -*-
#python 2.7.13
__metaclass__ = type
def confict(state, nextX):
  nextY = len(state)
  for i in range(nextY):
    if abs(state[i] - nextX) in (0, nextY - i):
      return True
  return False
def queens(num=8, state=()):
  for pos in range(num):
    if not confict(state, pos):
      if len(state) == num -1:
        yield (pos,)
      else:
        for result in queens(num, state + (pos,)):
          yield (pos,) + result
print list(queens()) #打印輸出

運(yùn)行結(jié)果：

[(0, 4, 7, 5, 2, 6, 1, 3), (0, 5, 7, 2, 6, 3, 1, 4), (0, 6, 3, 5, 7, 1, 4, 2), (0, 6, 4, 7, 1, 3, 5, 2), (1, 3, 5, 7, 2, 0, 6, 4), (1, 4, 6, 0, 2, 7, 5, 3), (1, 4, 6, 3, 0, 7, 5, 2), (1, 5, 0, 6, 3, 7, 2, 4), (1, 5, 7, 2, 0, 3, 6, 4), (1, 6, 2, 5, 7, 4, 0, 3), (1, 6, 4, 7, 0, 3, 5, 2), (1, 7, 5, 0, 2, 4, 6, 3), (2, 0, 6, 4, 7, 1, 3, 5), (2, 4, 1, 7, 0, 6, 3, 5), (2, 4, 1, 7, 5, 3, 6, 0), (2, 4, 6, 0, 3, 1, 7, 5), (2, 4, 7, 3, 0, 6, 1, 5), (2, 5, 1, 4, 7, 0, 6, 3), (2, 5, 1, 6, 0, 3, 7, 4), (2, 5, 1, 6, 4, 0, 7, 3), (2, 5, 3, 0, 7, 4, 6, 1), (2, 5, 3, 1, 7, 4, 6, 0), (2, 5, 7, 0, 3, 6, 4, 1), (2, 5, 7, 0, 4, 6, 1, 3), (2, 5, 7, 1, 3, 0, 6, 4), (2, 6, 1, 7, 4, 0, 3, 5), (2, 6, 1, 7, 5, 3, 0, 4), (2, 7, 3, 6, 0, 5, 1, 4), (3, 0, 4, 7, 1, 6, 2, 5), (3, 0, 4, 7, 5, 2, 6, 1), (3, 1, 4, 7, 5, 0, 2, 6), (3, 1, 6, 2, 5, 7, 0, 4), (3, 1, 6, 2, 5, 7, 4, 0), (3, 1, 6, 4, 0, 7, 5, 2), (3, 1, 7, 4, 6, 0, 2, 5), (3, 1, 7, 5, 0, 2, 4, 6), (3, 5, 0, 4, 1, 7, 2, 6), (3, 5, 7, 1, 6, 0, 2, 4), (3, 5, 7, 2, 0, 6, 4, 1), (3, 6, 0, 7, 4, 1, 5, 2), (3, 6, 2, 7, 1, 4, 0, 5), (3, 6, 4, 1, 5, 0, 2, 7), (3, 6, 4, 2, 0, 5, 7, 1), (3, 7, 0, 2, 5, 1, 6, 4), (3, 7, 0, 4, 6, 1, 5, 2), (3, 7, 4, 2, 0, 6, 1, 5), (4, 0, 3, 5, 7, 1, 6, 2), (4, 0, 7, 3, 1, 6, 2, 5), (4, 0, 7, 5, 2, 6, 1, 3), (4, 1, 3, 5, 7, 2, 0, 6), (4, 1, 3, 6, 2, 7, 5, 0), (4, 1, 5, 0, 6, 3, 7, 2), (4, 1, 7, 0, 3, 6, 2, 5), (4, 2, 0, 5, 7, 1, 3, 6), (4, 2, 0, 6, 1, 7, 5, 3), (4, 2, 7, 3, 6, 0, 5, 1), (4, 6, 0, 2, 7, 5, 3, 1), (4, 6, 0, 3, 1, 7, 5, 2), (4, 6, 1, 3, 7, 0, 2, 5), (4, 6, 1, 5, 2, 0, 3, 7), (4, 6, 1, 5, 2, 0, 7, 3), (4, 6, 3, 0, 2, 7, 5, 1), (4, 7, 3, 0, 2, 5, 1, 6), (4, 7, 3, 0, 6, 1, 5, 2), (5, 0, 4, 1, 7, 2, 6, 3), (5, 1, 6, 0, 2, 4, 7, 3), (5, 1, 6, 0, 3, 7, 4, 2), (5, 2, 0, 6, 4, 7, 1, 3), (5, 2, 0, 7, 3, 1, 6, 4), (5, 2, 0, 7, 4, 1, 3, 6), (5, 2, 4, 6, 0, 3, 1, 7), (5, 2, 4, 7, 0, 3, 1, 6), (5, 2, 6, 1, 3, 7, 0, 4), (5, 2, 6, 1, 7, 4, 0, 3), (5, 2, 6, 3, 0, 7, 1, 4), (5, 3, 0, 4, 7, 1, 6, 2), (5, 3, 1, 7, 4, 6, 0, 2), (5, 3, 6, 0, 2, 4, 1, 7), (5, 3, 6, 0, 7, 1, 4, 2), (5, 7, 1, 3, 0, 6, 4, 2), (6, 0, 2, 7, 5, 3, 1, 4), (6, 1, 3, 0, 7, 4, 2, 5), (6, 1, 5, 2, 0, 3, 7, 4), (6, 2, 0, 5, 7, 4, 1, 3), (6, 2, 7, 1, 4, 0, 5, 3), (6, 3, 1, 4, 7, 0, 2, 5), (6, 3, 1, 7, 5, 0, 2, 4), (6, 4, 2, 0, 5, 7, 1, 3), (7, 1, 3, 0, 6, 4, 2, 5), (7, 1, 4, 2, 0, 6, 3, 5), (7, 2, 0, 5, 1, 4, 6, 3), (7, 3, 0, 2, 5, 1, 6, 4)]

輸出列表長度：

print len(list(queens()))# 輸出：92

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