Question

python解决八皇后算法

Answer 1

global col #定义一些全局变量
global row
global pos_diag
global nag_diag
global count

def output():
''' 输出一种有效结果
'''
global count
print row
count += 1

def do_queen(i):
''' 生成所有正确解
@param i: 皇后的数目
'''
for j in range(0, 8): #依次尝试0～7位置
if col[j] == 1 and pos_diag[i-j+7] == 1 and nag_diag[i+j] == 1: #若该行，正对角线，负对角线上都没有皇后，则放入i皇后
row[i] = j
col[j] = 0 #调整各个列表状态
pos_diag[i-j+7] = 0
nag_diag[i+j] = 0
if i < 7:
do_queen(i+1) #可递增或递减
else:
output() #产生一个结果，输出
col[j] = 1 #恢复各个列表状态为之前的
pos_diag[i-j+7] = 1
nag_diag[i+j] = 1

if __name__ == '__main__':
col = [] #矩阵列的列表，存储皇后所在列，若该列没有皇后，则相应置为1，反之则0
row = [] #矩阵行的列表，存放每行皇后所在的列位置，随着程序的执行，在不断的变化中，之间输出结果
pos_diag = [] #正对角线，i-j恒定，-7~0~7，并且b(i)+7统一到0～14
nag_diag = [] #负对角线，i+j恒定，0～14
count = 0
for index in range(0, 8): #一些初始化工作
col.append(1)
row.append(0)
for index in range(0, 15):
pos_diag.append(1)
nag_diag.append(1)
do_queen(0) #开始递归，先放一个，依次递增，反过来，从7开始递减也可
print 'Totally have %d solutions!' % count

输出：
[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]
Totally have 92 solutions!

Answer 2

from itertools import permutations

n = 8

cols = range(n)

for vec in permutations(cols):

if (n == len(set(vec[i]+i for i in cols))

== len(set(vec[i]-i for i in cols))):

print vec