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grocery

First, you must install ortools package in this colab.

%pip install ortools

Grocery problem in Google CP Solver.

From Christian Schulte, Gert Smolka, Finite Domain http://www.mozart-oz.org/documentation/fdt/ Constraint Programming in Oz. A Tutorial. 2001. ''' A kid goes into a grocery store and buys four items. The cashier charges $7.11, the kid pays and is about to leave when the cashier calls the kid back, and says 'Hold on, I multiplied the four items instead of adding them; I'll try again; Hah, with adding them the price still comes to $7.11'. What were the prices of the four items? '''

Compare with the following models:

• MiniZinc: http://hakank.org/minizinc/grocery.mzn
• Comet: http://hakank.org/comet/grocery.co
• Zinc: http://hakank.org/minizinc/grocery.zinc

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

import sys

from ortools.constraint_solver import pywrapcp
from functools import reduce


def main():

  # Create the solver.
  solver = pywrapcp.Solver("Grocery")

  #
  # data
  #
  n = 4
  c = 711

  #
  # declare variables
  #
  item = [solver.IntVar(0, c, "item[%i]" % i) for i in range(n)]

  #
  # constraints
  #
  solver.Add(solver.Sum(item) == c)
  solver.Add(reduce(lambda x, y: x * y, item) == c * 100**3)

  # symmetry breaking
  for i in range(1, n):
    solver.Add(item[i - 1] < item[i])

  #
  # search and result
  #
  db = solver.Phase(item, solver.INT_VAR_SIMPLE, solver.INT_VALUE_SIMPLE)

  solver.NewSearch(db)
  num_solutions = 0
  while solver.NextSolution():
    print("item:", [item[i].Value() for i in range(n)])
    print()
    num_solutions += 1

  solver.EndSearch()

  print()
  print("num_solutions:", num_solutions)
  print("failures:", solver.Failures())
  print("branches:", solver.Branches())
  print("WallTime:", solver.WallTime())


main()