# 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 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()