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marathon2

<table align="left"> <td> <a href="https://colab.research.google.com/github/google/or-tools/blob/main/examples/notebook/contrib/marathon2.ipynb">Run in Google Colab</a> </td> <td> <a href="https://github.com/google/or-tools/blob/main/examples/contrib/marathon2.py">View source on GitHub</a> </td> </table>

First, you must install ortools package in this colab.

python

%pip install ortools

Marathon puzzle in Google CP Solver.

From Xpress example http://www.dashoptimization.com/home/cgi-bin/example.pl?id=mosel_puzzle_5_3 ''' Dominique, Ignace, Naren, Olivier, Philippe, and Pascal have arrived as the first six at the Paris marathon. Reconstruct their arrival order from the following information: a) Olivier has not arrived last b) Dominique, Pascal and Ignace have arrived before Naren and Olivier c) Dominique who was third last year has improved this year. d) Philippe is among the first four. e) Ignace has arrived neither in second nor third position. f) Pascal has beaten Naren by three positions. g) Neither Ignace nor Dominique are on the fourth position.

 (c) 2002 Dash Associates
author: S. Heipcke, Mar. 2002

'''

Compare with the following models:

MiniZinc: http://www.hakank.org/minizinc/marathon2.mzn
SICStus Prolog: http://www.hakank.org/sicstus/marathon2.pl
ECLiPSe: http://hakank.org/eclipse/marathon2.ecl
Gecode: http://hakank.org/gecode/marathon2.cpp

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

python

import sys
from ortools.constraint_solver import pywrapcp


def main():

  # Create the solver.
  solver = pywrapcp.Solver('Marathon')

  #
  # data
  #
  n = 6

  runners_str = [
      'Dominique', 'Ignace', 'Naren', 'Olivier', 'Philippe', 'Pascal'
  ]

  #
  # declare variables
  #
  runners = [solver.IntVar(1, n, 'runners[%i]' % i) for i in range(n)]
  Dominique, Ignace, Naren, Olivier, Philippe, Pascal = runners

  #
  # constraints
  #
  solver.Add(solver.AllDifferent(runners))

  # a: Olivier not last
  solver.Add(Olivier != n)

  # b: Dominique, Pascal and Ignace before Naren and Olivier
  solver.Add(Dominique < Naren)
  solver.Add(Dominique < Olivier)
  solver.Add(Pascal < Naren)
  solver.Add(Pascal < Olivier)
  solver.Add(Ignace < Naren)
  solver.Add(Ignace < Olivier)

  # c: Dominique better than third
  solver.Add(Dominique < 3)

  # d: Philippe is among the first four
  solver.Add(Philippe <= 4)

  # e: Ignace neither second nor third
  solver.Add(Ignace != 2)
  solver.Add(Ignace != 3)

  # f: Pascal three places earlier than Naren
  solver.Add(Pascal + 3 == Naren)

  # g: Neither Ignace nor Dominique on fourth position
  solver.Add(Ignace != 4)
  solver.Add(Dominique != 4)

  #
  # solution and search
  #
  db = solver.Phase(runners, solver.CHOOSE_MIN_SIZE_LOWEST_MIN,
                    solver.ASSIGN_CENTER_VALUE)

  solver.NewSearch(db)

  num_solutions = 0
  while solver.NextSolution():
    num_solutions += 1
    runners_val = [runners[i].Value() for i in range(n)]
    print('runners:', runners_val)
    print('Places:')
    for i in range(1, n + 1):
      for j in range(n):
        if runners_val[j] == i:
          print('%i: %s' % (i, runners_str[j]))
    print()

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


main()