112 lines
3.1 KiB
C#
112 lines
3.1 KiB
C#
//
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// Copyright 2012 Hakan Kjellerstrand
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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using System;
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using Google.OrTools.ConstraintSolver;
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public class Grocery
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{
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public static void Decreasing(Solver solver, IntVar[] x)
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{
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for (int i = 0; i < x.Length - 1; i++)
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{
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solver.Add(x[i] <= x[i + 1]);
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}
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}
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//
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// Simple decomposition of Prod() for an IntVar array
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//
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private static Constraint MyProd(IntVar[] x, int prod)
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{
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int len = x.Length;
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IntVar[] tmp = new IntVar[len];
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tmp[0] = x[0];
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for (int i = 1; i < len; i++)
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{
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tmp[i] = (tmp[i - 1] * x[i]).Var();
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}
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return tmp[len - 1] == prod;
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}
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/**
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*
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* Grocery problem.
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*
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* From Christian Schulte, Gert Smolka, Finite Domain
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* http://www.mozart-oz.org/documentation/fdt/
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* Constraint Programming in Oz. A Tutorial. 2001.
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* """
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* A kid goes into a grocery store and buys four items. The cashier
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* charges $7.11, the kid pays and is about to leave when the cashier
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* calls the kid back, and says 'Hold on, I multiplied the four items
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* instead of adding them; I'll try again; Hah, with adding them the
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* price still comes to $7.11'. What were the prices of the four items?
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* """
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*
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*/
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private static void Solve()
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{
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Solver solver = new Solver("Grocery");
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int n = 4;
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int c = 711;
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//
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// Decision variables
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//
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IntVar[] item = solver.MakeIntVarArray(n, 0, c / 2, "item");
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//
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// Constraints
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//
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solver.Add(item.Sum() == c);
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// solver.Add(item[0] * item[1] * item[2] * item[3] == c * 100*100*100);
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// solver.Add(item.Prod() == c * 100*100*100);
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solver.Add(MyProd(item, c * 100 * 100 * 100));
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// Symmetry breaking
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Decreasing(solver, item);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(item, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MIN_VALUE);
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solver.NewSearch(db);
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while (solver.NextSolution())
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{
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for (int i = 0; i < n; i++)
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{
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Console.Write(item[i].Value() + " ");
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}
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Console.WriteLine();
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}
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Console.WriteLine("\nWallTime: " + solver.WallTime() + "ms ");
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Console.WriteLine("Failures: " + solver.Failures());
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Console.WriteLine("Branches: " + solver.Branches());
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solver.EndSearch();
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}
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public static void Main(String[] args)
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{
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Solve();
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}
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}
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