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#!/usr/bin/env python
# -*- coding: iso-8859-1 -*-
# copyright 2002-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of logilab-constraint.
#
# logilab-constraint is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# logilab-constraint is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-constraint. If not, see <http://www.gnu.org/licenses/>.
"""N queens problem
The problem is solved with a EnumeratorDistributor splitting
the smallest domain in at most N subdomains."""
from __future__ import generators
from logilab.constraint import *
from logilab.constraint.distributors import *
from chess import ChessDomain, QueensConstraint
def queens(size=8,verbose=0):
variables = []
domains = {}
constraints = []
for i in range(size):
name = 'Q%02d'%i
variables.append(name)
domains[name] = ChessDomain(size)
for q1 in variables:
for q2 in variables:
if q1 < q2:
c = QueensConstraint((q1,q2))
constraints.append(c)
r = Repository(variables,domains,constraints)
for sol in Solver(EnumeratorDistributor()).solve_all(r,verbose):
yield sol
def draw_solution(s):
size = len(s)
queens = {}
board = ''
for q,p in s.items():
queens[p]=q
board += '_'*(size*2+1)+'\n'
for i in range(size):
#
for j in range(size):
q = queens.get((i,j))
if q is None:
board+='|'+'-'[(i+j)%2]
else:
board+='|Q'
board+='|\n'
board += ''*(size*2+1)
print board
def main(args = None):
import sys,getopt
if args is None:
args = sys.argv[1:]
opts,args = getopt.getopt(args,'dvf')
display = 0
verbose = 0
first = 0
if args:
size = int(args[0])
else:
size = 8
for o,v in opts:
if o == '-d':
display = 1
elif o == '-v':
verbose += 1
elif o == "-f":
first = 1
count = 0
for sol in queens(size,verbose):
count += 1
if display:
print 'solution #%d'%count
draw_solution(sol)
print '*'*80
if first:
break
if not display:
print 'Use -d option to display solutions'
print count,'solutions found.'
if __name__ == '__main__':
## import hotshot
## p = hotshot.Profile('/tmp/queens.prof')
## p.runcall(main)
## p.close()
main()
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