ó
Afc@sBdZd
Z
ddd„ƒYZd„Zedkr>eƒ
ndS(s¹N queens problem.

The (well-known) problem is due to Niklaus Wirth.

This solution is inspired by Dijkstra (Structured Programming).  It is
a classic recursive backtracking approach.

itQueenscBsSeZ
ed„
Zd
„Zdd„
Zd„Zd„Zd„ZdZ	d„Z
RS(cCs|
|_|j
ƒ
dS(
N(t
ntreset(tselfR
((s+/usr/lib64/python2.7/Demo/scripts/queens.pyt__init__s
	
c
Csf|j}
dg
|
|_d
g
|
|_d
g
d|
d|_d
g
d|
d|_d
|_dS(Niii
(R
tNonet
ytrowtuptdowntnfound(RR
((s+/usr/lib64/python2.7/Demo/scripts/queens.pyRs
	




icCs„x}t|j
ƒ
D]l}|j|
|ƒr|j|
|ƒ
|
d
|j
krX|jƒ
n|j|
d
ƒ

|j|
|ƒ
qqWdS(Ni
(trangeR
tsafetplacetdisplaytsolvetremove(Rt
xR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyRs






cCs0|j|o/|j
|
|o/|j|
|S(
N(RRR	(RRR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyR&s
cCs@||j|
<d
|j
|<d
|j|
|<d
|j|
|<dS(Ni
(RRRR	(RRR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyR
)s





cCs@d|j
|
<d
|j|<d
|j|
|<d
|j|
|<dS(Ni(RRRRR	(RRR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyR/s





c
Cs®|jd
|_|j
rdSdd|jdGHxbt|jd
ddƒD]G}
dGx5t|jƒ
D]$}|j||
kr…dGqedGqeWdGHqKWdd|jdGHdS(	Ni
s+-s--t
+iÿÿÿÿt
|t
Qt
.(R
tsilentR
RR(RRR((s+/usr/lib64/python2.7/Demo/scripts/queens.pyR7s

	


 




	
(t__name__t
__module__t
NRRRRR
RRR(((s+/usr/lib64/python2.7/Demo/scripts/queens.pyRs	
			cCsšd
dl}d}
t
}|jdd!dg
krDd}
|jd=n|jdrgt|jdƒ
}nt|ƒ
}|
|_|jƒ
dG|jGdGHdS(Niÿÿÿÿii
is-ntFounds
solutions.(tsysRtargvtintRRRR
(RRR
t
q((s+/usr/lib64/python2.7/Demo/scripts/queens.pytmainFs











	


t__main__N((t__doc__RRRR(((s+/usr/lib64/python2.7/Demo/scripts/queens.pyt<module>
s
8