88 lines
2.5 KiB
Python
88 lines
2.5 KiB
Python
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# Copyright 2010-2011 Google
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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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Cryptoarithmetic puzzle
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First attempt to solve equation CP + IS + FUN = TRUE
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where each letter represents a unique digit.
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This problem has 72 different solutions in base 10.
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Use of NewSearch.
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"""
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from constraint_solver import pywrapcp
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from os import abort
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def CPIsFun():
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# Constraint programming engine
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solver = pywrapcp.Solver('CP is fun!');
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kBase = 10
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# Decision variables
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digits = range(0, kBase)
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digits_without_zero = digits[1:]
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c = solver.IntVar(digits_without_zero, 'C');
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p = solver.IntVar(digits, 'P');
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i = solver.IntVar(digits_without_zero, 'I');
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s = solver.IntVar(digits, 'S');
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f = solver.IntVar(digits_without_zero, 'F');
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u = solver.IntVar(digits, 'U');
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n = solver.IntVar(digits, 'N');
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t = solver.IntVar(digits_without_zero, 'T');
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r = solver.IntVar(digits, 'R');
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e = solver.IntVar(digits, 'E');
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# We need to group variables in a list to be able to use
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# the global constraint AllDifferent
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letters = [c, p, i, s, f, u, n, t, r, e]
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# Check if we have enough digits
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assert kBase >= len(letters)
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# Constraints
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solver.Add(solver.AllDifferent(letters))
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# CP + IS + FUN = TRUE
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term1 = solver.Sum([kBase*c, p])
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term2 = solver.Sum([kBase*i, s])
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term3 = solver.Sum([kBase*kBase*f, kBase*u, n])
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sum_terms = solver.Sum([term1, term2, term3])
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sum_value = solver.Sum([kBase*kBase*kBase*t, kBase*kBase*r, kBase*u, e])
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solver.Add(sum_terms == sum_value)
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db = solver.Phase(letters, solver.INT_VAR_DEFAULT,
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solver.INT_VALUE_DEFAULT)
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solver.NewSearch(db)
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if solver.NextSolution():
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print letters
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# Is CP + IS + FUN = TRUE?
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assert (kBase*c.Value() + p.Value() + kBase*i.Value() + s.Value() +
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kBase*kBase*f.Value() + kBase*u.Value() + n.Value() ==
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kBase*kBase*kBase*t.Value() + kBase*kBase*r.Value() +
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kBase*u.Value() + e.Value())
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else:
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print 'Cannot solve problem.'
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solver.EndSearch()
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return
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if __name__ == '__main__':
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CPIsFun()
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