Python基础基础教程中，第九章讲到了八皇后，书中的代码中迭代器、生成器、递归的使用比较难理解，对代码进行了就修改以方便理解。
书中的解决方案
def conflict(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
=()):
print('start:',state
)
for pos
in range(num
):
if not conflict
(state
, pos
):
if len(state
) == num
-1:
print('last:',pos
)
yield (pos
,)
else:
for result
in queens
(num
, state
+ (pos
,)):
print('yield','inside:',state
,'pos:',pos
,'result:',result
)
yield (pos
,) + result
print('inside',state
,'end')
print(list(queens
(4)))
输出结果
start
: ()
start
: (0,)
start
: (0, 2)
inside
(0, 2) end
start
: (0, 3)
start
: (0, 3, 1)
inside
(0, 3, 1) end
inside
(0, 3) end
inside
(0,) end
start
: (1,)
start
: (1, 3)
start
: (1, 3, 0)
last
: 2
yield inside
: (1, 3) pos
: 0 result
: (2,)
yield inside
: (1,) pos
: 3 result
: (0, 2)
yield inside
: () pos
: 1 result
: (3, 0, 2)
inside
(1, 3, 0) end
inside
(1, 3) end
inside
(1,) end
start
: (2,)
start
: (2, 0)
start
: (2, 0, 3)
last
: 1
yield inside
: (2, 0) pos
: 3 result
: (1,)
yield inside
: (2,) pos
: 0 result
: (3, 1)
yield inside
: () pos
: 2 result
: (0, 3, 1)
inside
(2, 0, 3) end
inside
(2, 0) end
inside
(2,) end
start
: (3,)
start
: (3, 0)
start
: (3, 0, 2)
inside
(3, 0, 2) end
inside
(3, 0) end
start
: (3, 1)
inside
(3, 1) end
inside
(3,) end
inside
() end
[(1, 3, 0, 2), (2, 0, 3, 1)]
