text: # Copyright 2010 Hakan Kjellerstrand hakank@gmail.com
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """
  
    Scheduling speakers problem in Google CP Solver.
  
    From Rina Dechter, Constraint Processing, page 72
    Scheduling of 6 speakers in 6 slots.
  
    Compare with the following models:
    * MiniZinc: http://www.hakank.org/minizinc/scheduling_speakers.mzn
    * SICStus Prolog: http://www.hakank.org/sicstus/scheduling_speakers.pl
    * ECLiPSe: http://hakank.org/eclipse/scheduling_speakers.ecl
    * Gecode: http://hakank.org/gecode/scheduling_speakers.cpp
  
    This model was created by Hakan Kjellerstrand (hakank@gmail.com)
    Also see my other Google CP Solver models:
    http://www.hakank.org/google_or_tools/
  """
  from __future__ import print_function
  from ortools.constraint_solver import pywrapcp
  
  
  def main():
  
    # Create the solver.
    solver = pywrapcp.Solver('Scheduling speakers')
  
    #
    # data
    #
    n = 6  # number of speakers
  
    # slots available to speak
    available = [
        # Reasoning:
        [3, 4, 5, 6],  # 2) the only one with 6 after speaker F -> 1
        [3, 4],  # 5) 3 or 4
        [2, 3, 4, 5],  # 3) only with 5 after F -> 1 and A -> 6
        [2, 3, 4],  # 4) only with 2 after C -> 5 and F -> 1
        [3, 4],  # 5) 3 or 4
        [1, 2, 3, 4, 5, 6]  # 1) the only with 1
    ]
  
    #
    # variables
    #
    x = [solver.IntVar(1, n, 'x[%i]' % i) for i in range(n)]
  
    #
    # constraints
    #
    solver.Add(solver.AllDifferent(x))
  
    for i in range(n):
      solver.Add(solver.MemberCt(x[i], available[i]))
  
    #
    # search and result
    #
    db = solver.Phase(x, solver.INT_VAR_DEFAULT, solver.INT_VALUE_DEFAULT)
  
    solver.NewSearch(db)
  
    num_solutions = 0
  
    while solver.NextSolution():
      num_solutions += 1
      print('x:', [x[i].Value() for i in range(n)])
  
    solver.EndSearch()
  
    print()
    print('num_solutions:', num_solutions)
    print('failures:', solver.Failures())
    print('branches:', solver.Branches())
    print('WallTime:', solver.WallTime(), 'ms')
  
  
  if __name__ == '__main__':
    main()
  