113 lines
2.8 KiB
Python
113 lines
2.8 KiB
Python
# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.com
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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n-queens problem in Google CP Solver.
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N queens problem.
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Faster than the previous versions:
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- http://www.hakank.org/gogle_cp_solver/nqueens.py
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- http://www.hakank.org/gogle_cp_solver/nqueens2.py
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This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
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Also see my other Google CP Solver models: http://www.hakank.org/google_or_tools/
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"""
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import sys, string
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from constraint_solver import pywrapcp
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def main(n=8, num_sol=0, print_sol=1):
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# Create the solver.
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solver = pywrapcp.Solver('n-queens')
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#
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# data
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#
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print "n:", n
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print "num_sol:", num_sol
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print "print_sol:", print_sol
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# declare variables
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q = [solver.IntVar(0,n-1, 'x%i' % i) for i in range(n)]
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#
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# constraints
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#
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solver.Add(solver.AllDifferent(q))
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solver.Add(solver.AllDifferent([q[i]+i for i in range(n)]))
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solver.Add(solver.AllDifferent([q[i]-i for i in range(n)]))
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# symmetry breaking
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# solver.Add(q[0] == 0)
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#
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# search
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#
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db = solver.Phase(q,
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solver.CHOOSE_MIN_SIZE_LOWEST_MAX,
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solver.ASSIGN_CENTER_VALUE)
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solver.NewSearch(db)
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num_solutions = 0
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while solver.NextSolution():
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if print_sol:
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qval = [q[i].Value() for i in range(n)]
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print "q:", qval
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for i in range(n):
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for j in range(n):
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if qval[i] == j:
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print "Q",
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else:
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print "_",
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print
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print
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num_solutions += 1
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if num_sol > 0 and num_solutions >= num_sol:
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break
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solver.EndSearch()
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print
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print "num_solutions:", num_solutions
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print "failures:", solver.Failures()
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print "branches:", solver.Branches()
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print "WallTime:", solver.WallTime(), "ms"
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n = 8
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num_sol = 0
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print_sol = 1
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if __name__ == '__main__':
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if len(sys.argv) > 1:
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n = int(sys.argv[1])
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if len(sys.argv) > 2:
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num_sol = int(sys.argv[2])
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if len(sys.argv) > 3:
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print_sol = int(sys.argv[3])
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main(n, num_sol, print_sol)
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# print_sol = False
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# show_all = False
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# for n in range(1000,1001):
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# print
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# main(n, num_sol, print_sol)
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