2025-01-10 11:35:44 +01:00
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// Copyright 2010-2025 Google LLC
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2012-01-25 18:02:25 +00:00
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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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2014-07-09 15:18:27 +00:00
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2012-01-25 18:02:25 +00:00
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using System;
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using Google.OrTools.Graph;
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2020-11-03 10:04:19 +01:00
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public class CsFlow
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{
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private static void SolveMaxFlow()
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{
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Console.WriteLine("Max Flow Problem");
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int numNodes = 6;
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int numArcs = 9;
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int[] tails = { 0, 0, 0, 0, 1, 2, 3, 3, 4 };
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int[] heads = { 1, 2, 3, 4, 3, 4, 4, 5, 5 };
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int[] capacities = { 5, 8, 5, 3, 4, 5, 6, 6, 4 };
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int[] expectedFlows = { 4, 4, 2, 0, 4, 4, 0, 6, 4 };
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int expectedTotalFlow = 10;
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MaxFlow maxFlow = new MaxFlow();
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for (int i = 0; i < numArcs; ++i)
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{
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int arc = maxFlow.AddArcWithCapacity(tails[i], heads[i], capacities[i]);
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if (arc != i)
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throw new Exception("Internal error");
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}
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int source = 0;
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int sink = numNodes - 1;
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Console.WriteLine("Solving max flow with " + numNodes + " nodes, and " + numArcs + " arcs, source=" + source +
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", sink=" + sink);
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MaxFlow.Status solveStatus = maxFlow.Solve(source, sink);
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if (solveStatus == MaxFlow.Status.OPTIMAL)
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{
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long totalFlow = maxFlow.OptimalFlow();
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Console.WriteLine("total computed flow " + totalFlow + ", expected = " + expectedTotalFlow);
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for (int i = 0; i < numArcs; ++i)
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{
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Console.WriteLine("Arc " + i + " (" + maxFlow.Head(i) + " -> " + maxFlow.Tail(i) +
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"), capacity = " + maxFlow.Capacity(i) + ") computed = " + maxFlow.Flow(i) +
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", expected = " + expectedFlows[i]);
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}
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}
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else
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{
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Console.WriteLine("Solving the max flow problem failed. Solver status: " + solveStatus);
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}
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2014-07-09 12:21:55 +00:00
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}
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2020-11-03 10:04:19 +01:00
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private static void SolveMinCostFlow()
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{
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Console.WriteLine("Min Cost Flow Problem");
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int numSources = 4;
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int numTargets = 4;
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int[,] costs = { { 90, 75, 75, 80 }, { 35, 85, 55, 65 }, { 125, 95, 90, 105 }, { 45, 110, 95, 115 } };
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int expectedCost = 275;
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MinCostFlow minCostFlow = new MinCostFlow();
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for (int source = 0; source < numSources; ++source)
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{
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for (int target = 0; target < numTargets; ++target)
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{
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minCostFlow.AddArcWithCapacityAndUnitCost(source, /*target=*/numSources + target,
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/*capacity=*/1,
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/*flow unit cost=*/costs[source, target]);
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}
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}
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for (int source = 0; source < numSources; ++source)
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{
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minCostFlow.SetNodeSupply(source, 1);
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}
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for (int target = 0; target < numTargets; ++target)
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{
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minCostFlow.SetNodeSupply(numSources + target, -1);
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}
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Console.WriteLine("Solving min cost flow with " + numSources + " sources, and " + numTargets + " targets.");
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MinCostFlow.Status solveStatus = minCostFlow.Solve();
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if (solveStatus == MinCostFlow.Status.OPTIMAL)
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{
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Console.WriteLine("total computed flow cost = " + minCostFlow.OptimalCost() +
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", expected = " + expectedCost);
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}
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else
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{
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Console.WriteLine("Solving the min cost flow problem failed." + " Solver status: " + solveStatus);
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}
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2012-01-25 18:02:25 +00:00
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}
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2020-11-03 10:04:19 +01:00
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static void Main()
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{
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SolveMaxFlow();
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SolveMinCostFlow();
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}
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2012-01-25 18:02:25 +00:00
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}
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