8927b03942
Some of these imports are not used. The rest of them only import string to use the string.atoi function. But string.atoi(s) on a string input is identical to just int(s). See the docs: "deprecated since 2.0".
107 lines
2.6 KiB
Python
107 lines
2.6 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:
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http://www.hakank.org/google_or_tools/
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"""
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import sys
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from ortools.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))
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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_MIN_VALUE
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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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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 "WallTime:", solver.WallTime()
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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 = int(sys.argv[1])
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main(n)
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