# 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.
"""
xkcd problem (Knapsack) in Google CP Solver.
http://xkcd.com/287/
Some amount (or none) of each dish should be ordered to give a total
of exact 15.05
Compare with the following models:
* Comet: http://www.hakank.org/comet/xkcd.co
* ECLiPSE: http://www.hakank.org/eclipse/xkcd.ecl
* Gecode: http://www.hakank.org/gecode/xkcd.cpp
* Gecode/R: http://www.hakank.org/gecode_r/xkcd.rb
* MiniZinc: http://www.hakank.org/minizinc/xkcd.mzn
* Tailor: http://www.hakank.org/minizinc/xkcd.mzn
* SICtus: http://www.hakank.org/sicstus/xkcd.pl
* Zinc: http://www.hakank.org/minizinc/xkcd.zinc
This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
Also see my other Google CP Solver models:
http://www.hakank.org/google_cp_solver/
"""
from ortools.constraint_solver import pywrapcp
def main():
# Create the solver.
solver = pywrapcp.Solver("xkcd knapsack")
#
# data
#
num_prices = 6
# for price and total: multiplied by 100 to be able to use integers
price = [215, 275, 335, 355, 420, 580]
total = 1505
products = ["mixed fruit", "french fries", "side salad",
"host wings", "mozzarella sticks", "samples place"]
# declare variables
# how many items of each dish
x = [solver.IntVar(0, 10, "x%i" % i) for i in range(num_prices)]
z = solver.IntVar(0, 1505, "z")
#
# constraints
#
solver.Add(z == solver.Sum([x[i] * price[i] for i in range(num_prices)]))
solver.Add(z == total)
#
# solution and search
#
solution = solver.Assignment()
solution.Add([x[i] for i in range(num_prices)])
solution.Add(z)
collector = solver.AllSolutionCollector(solution)
# collector = solver.FirstSolutionCollector(solution)
# search_log = solver.SearchLog(100, x[0])
solver.Solve(solver.Phase([x[i] for i in range(num_prices)],
solver.INT_VAR_SIMPLE,
solver.ASSIGN_MIN_VALUE),
[collector])
num_solutions = collector.SolutionCount()
print "num_solutions: ", num_solutions
if num_solutions > 0:
for s in range(num_solutions):
print "z:", collector.Value(s, z)
xval = [collector.Value(s, x[i]) for i in range(num_prices)]
print "x:", xval
for i in range(num_prices):
if xval[i] > 0:
print xval[i], "of", products[i], ":", price[i] / 100.0
print
print
print "num_solutions:", num_solutions
print "failures:", solver.Failures()
print "branches:", solver.Branches()
print "WallTime:", solver.WallTime()
else:
print "No solutions found"
if __name__ == "__main__":
main()