107 lines
2.9 KiB
Python
107 lines
2.9 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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Magic squares in Google CP Solver.
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Magic square problem.
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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 string, sys
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from constraint_solver import pywrapcp
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def main(n=4):
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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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#
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# declare variables
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#
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x = {}
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for i in range(n):
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for j in range(n):
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x[(i, j)] = solver.IntVar(1, n*n, 'x(%i,%i)' % (i, j))
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x_flat = [x[(i,j)] for i in range(n) for j in range(n)]
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# the sum
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# s = ( n * (n*n + 1)) / 2
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s = solver.IntVar(1, n*n*n,'s')
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#
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# constraints
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#
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# solver.Add(s == ( n * (n*n + 1)) / 2)
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solver.Add(solver.AllDifferent(x_flat, True))
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[solver.Add(solver.Sum([x[(i,j)] for j in range(n)]) == s) for i in range(n)]
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[solver.Add(solver.Sum([x[(i,j)] for i in range(n)]) == s) for j in range(n)]
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solver.Add(solver.Sum([ x[(i,i)] for i in range(n)]) == s) # diag 1
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solver.Add(solver.Sum([ x[(i,n-i-1)] for i in range(n)]) == s) # diag 2
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# symmetry breaking
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# solver.Add(x[(0,0)] == 1)
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#
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# solution and search
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#
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solution = solver.Assignment()
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solution.Add(x_flat)
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solution.Add(s)
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# db: DecisionBuilder
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db = solver.Phase(x_flat,
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#solver.INT_VAR_DEFAULT,
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solver.CHOOSE_FIRST_UNBOUND,
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#solver.CHOOSE_MIN_SIZE_LOWEST_MAX,
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solver.ASSIGN_CENTER_VALUE
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#solver.ASSIGN_MIN_VALUE
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)
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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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print "s:", s.Value()
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for i in range(n):
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for j in range(n):
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print "%2i" % x[(i,j)].Value(),
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print
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print
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num_solutions += 1
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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 "wall_time:", solver.wall_time()
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n = 4
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if __name__ == '__main__':
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if len(sys.argv) > 1:
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n = string.atoi(sys.argv[1])
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main(n)
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