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.
  """
  
    Place number puzzle Google CP Solver.
  
    http://ai.uwaterloo.ca/~vanbeek/Courses/Slides/introduction.pdf
    '''
    Place numbers 1 through 8 on nodes
    - each number appears exactly once
    - no connected nodes have consecutive numbers
         2 - 5
       / | X | \
     1 - 3 - 6 - 8
       \ | X | /
         4 - 7
    ""
  
    Compare with the following models:
    * MiniZinc: http://www.hakank.org/minizinc/place_number.mzn
    * Comet: http://www.hakank.org/comet/place_number_puzzle.co
    * ECLiPSe: http://www.hakank.org/eclipse/place_number_puzzle.ecl
    * SICStus Prolog: http://www.hakank.org/sicstus/place_number_puzzle.pl
    * Gecode: http://www.hakank.org/gecode/place_number_puzzle.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/
  
  """
  import sys
  from ortools.constraint_solver import pywrapcp
  
  
  def main():
  
    # Create the solver.
    solver = pywrapcp.Solver("Place number")
  
    # data
    m = 32
    n = 8
    # Note: this is 1-based for compatibility (and lazyness)
    graph = [[1, 2], [1, 3], [1, 4], [2, 1], [2, 3], [2, 5], [2, 6], [3, 2],
             [3, 4], [3, 6], [3, 7], [4, 1], [4, 3], [4, 6], [4, 7], [5, 2],
             [5, 3], [5, 6], [5, 8], [6, 2], [6, 3], [6, 4], [6, 5], [6, 7],
             [6, 8], [7, 3], [7, 4], [7, 6], [7, 8], [8, 5], [8, 6], [8, 7]]
  
    # declare variables
    x = [solver.IntVar(1, n, "x%i" % i) for i in range(n)]
  
    #
    # constraints
    #
    solver.Add(solver.AllDifferent(x))
    for i in range(m):
      # Note: make 0-based
      solver.Add(abs(x[graph[i][0] - 1] - x[graph[i][1] - 1]) > 1)
  
    # symmetry breaking
    solver.Add(x[0] < x[n - 1])
  
    #
    # solution and search
    #
    solution = solver.Assignment()
    solution.Add(x)
  
    collector = solver.AllSolutionCollector(solution)
  
    solver.Solve(
        solver.Phase(x, solver.CHOOSE_FIRST_UNBOUND, solver.ASSIGN_MIN_VALUE),
        [collector])
  
    num_solutions = collector.SolutionCount()
    for s in range(num_solutions):
      print("x:", [collector.Value(s, x[i]) for i in range(len(x))])
  
    print()
    print("num_solutions:", num_solutions)
    print("failures:", solver.Failures())
    print("branches:", solver.Branches())
    print("WallTime:", solver.WallTime())
    print()
  
  
  if __name__ == "__main__":
    main()
  