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xkcd

examples/notebook/contrib/xkcd.ipynb

2016-063.7 KB
Original Source
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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

<table align="left"> <td> <a href="https://colab.research.google.com/github/google/or-tools/blob/main/examples/notebook/contrib/xkcd.ipynb">Run in Google Colab</a> </td> <td> <a href="https://github.com/google/or-tools/blob/main/examples/contrib/xkcd.py">View source on GitHub</a> </td> </table>

First, you must install ortools package in this colab.

python
%pip install ortools

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:

This model was created by Hakan Kjellerstrand ([email protected]) Also see my other Google CP Solver models: http://www.hakank.org/google_cp_solver/

python
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) / 100.0)
      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")


main()