119 lines
3.0 KiB
C#
119 lines
3.0 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 System.Collections;
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using System.Collections.Generic;
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using System.Linq;
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using Google.OrTools.ConstraintSolver;
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public class SubsetSum
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{
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public static IntVar[] subset_sum(Solver solver,
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int[] values,
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int total) {
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int n = values.Length;
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IntVar[] x = solver.MakeIntVarArray(n, 0, n, "x");
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solver.Add(x.ScalProd(values) == total);
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return x;
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}
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/**
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*
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* Subset sum problem.
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*
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* From Katta G. Murty: 'Optimization Models for Decision Making', page 340
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* http://ioe.engin.umich.edu/people/fac/books/murty/opti_model/junior-7.pdf
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* """
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* Example 7.8.1
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*
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* A bank van had several bags of coins, each containing either
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* 16, 17, 23, 24, 39, or 40 coins. While the van was parked on the
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* street, thieves stole some bags. A total of 100 coins were lost.
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* It is required to find how many bags were stolen.
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* """
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*
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* Also see http://www.hakank.org/or-tools/subset_sum.py
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*
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*/
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private static void Solve(int[] coins, int total)
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{
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Solver solver = new Solver("SubsetSum");
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int n = coins.Length;
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Console.Write("Coins: ");
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for(int i = 0; i < n; i++) {
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Console.Write(coins[i] + " ");
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}
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Console.WriteLine("\nTotal: {0}", total);
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//
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// Variables
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//
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// number of coins
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IntVar s = solver.MakeIntVar(0, coins.Sum(), "s");
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//
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// Constraints
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//
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IntVar[] x = subset_sum(solver, coins, total);
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solver.Add(x.Sum() == s);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(x,
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Solver.CHOOSE_FIRST_UNBOUND,
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Solver.ASSIGN_MIN_VALUE);
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solver.NewSearch(db);
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while (solver.NextSolution()) {
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Console.Write("x: ");
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for(int i = 0; i < n; i++) {
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Console.Write(x[i].Value() + " ");
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}
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Console.WriteLine(" s: {0}", s.Value());
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}
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Console.WriteLine("\nSolutions: {0}", solver.Solutions());
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Console.WriteLine("WallTime: {0}ms", solver.WallTime());
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Console.WriteLine("Failures: {0}", solver.Failures());
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Console.WriteLine("Branches: {0} ", 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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int[] coins = {16, 17, 23, 24, 39, 40};
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int total = 100;
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if (args.Length > 0) {
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total = Convert.ToInt32(args[0]);
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}
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Solve(coins, total);
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}
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}
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