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# 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/

"""
from __future__ import print_function
import sys
from ortools.constraint_solver import pywrapcp



# 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()