# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.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@bonetmail.com)
  Also see my other Google CP Solver models: http://www.hakank.org/google_or_tools/

"""

import sys
import string
from 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()