102 lines
2.8 KiB
C#
102 lines
2.8 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.IO;
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using System.Linq;
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using System.Text.RegularExpressions;
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using Google.OrTools.ConstraintSolver;
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public class SetCovering
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{
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/**
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*
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* Solves a set covering problem.
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* See See http://www.hakank.org/or-tools/set_covering.py
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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("SetCovering");
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//
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// data
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//
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// Placing of firestations, from Winston 'Operations Research',
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// page 486.
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int min_distance = 15;
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int num_cities = 6;
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int[,] distance = { { 0, 10, 20, 30, 30, 20 }, { 10, 0, 25, 35, 20, 10 }, { 20, 25, 0, 15, 30, 20 },
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{ 30, 35, 15, 0, 15, 25 }, { 30, 20, 30, 15, 0, 14 }, { 20, 10, 20, 25, 14, 0 } };
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//
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// Decision variables
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//
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IntVar[] x = solver.MakeIntVarArray(num_cities, 0, 1, "x");
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IntVar z = x.Sum().Var();
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//
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// Constraints
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//
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// ensure that all cities are covered
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for (int i = 0; i < num_cities; i++)
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{
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IntVar[] b = (from j in Enumerable.Range(0, num_cities)
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where distance[i, j] <= min_distance select x[j])
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.ToArray();
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solver.Add(b.Sum() >= 1);
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}
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//
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// objective
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//
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OptimizeVar objective = z.Minimize(1);
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(x, Solver.INT_VAR_DEFAULT, Solver.INT_VALUE_DEFAULT);
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solver.NewSearch(db, objective);
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while (solver.NextSolution())
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{
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Console.WriteLine("z: {0}", z.Value());
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Console.Write("x: ");
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for (int i = 0; i < num_cities; i++)
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{
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Console.Write(x[i].Value() + " ");
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}
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Console.WriteLine();
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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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Solve();
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}
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}
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