2025-01-10 11:35:44 +01:00
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// Copyright 2010-2025 Google LLC
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2011-03-29 13:53:49 +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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2022-10-05 18:33:10 +02:00
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2022-10-06 21:50:57 +02:00
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package com.google.ortools.java;
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2011-03-29 13:53:49 +00:00
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2020-09-11 21:17:23 +02:00
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import com.google.ortools.Loader;
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2012-01-10 14:16:39 +00:00
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import com.google.ortools.graph.MaxFlow;
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import com.google.ortools.graph.MinCostFlow;
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2011-03-29 13:53:49 +00:00
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2022-10-05 18:33:10 +02:00
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/**
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* Sample showing how to model using the flow solver.
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*/
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2019-05-06 10:31:03 +02:00
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public class FlowExample {
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2011-03-29 13:53:49 +00:00
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private static void solveMinCostFlow() {
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2014-07-09 11:26:55 +00:00
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System.out.println("Min Cost Flow Problem - Simple interface");
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2011-03-29 13:53:49 +00:00
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final int numSources = 4;
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final int numTargets = 4;
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2018-11-10 23:56:52 +01:00
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final int[][] costs = {
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{90, 75, 75, 80}, {35, 85, 55, 65}, {125, 95, 90, 105}, {45, 110, 95, 115}};
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final int expectedCost = 275;
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MinCostFlow minCostFlow = new MinCostFlow();
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2011-05-26 09:33:52 +00:00
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for (int source = 0; source < numSources; ++source) {
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for (int target = 0; target < numTargets; ++target) {
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2018-11-10 23:56:52 +01:00
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minCostFlow.addArcWithCapacityAndUnitCost(
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source, numSources + target, 1, costs[source][target]);
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}
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}
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for (int node = 0; node < numSources; ++node) {
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minCostFlow.setNodeSupply(node, 1);
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minCostFlow.setNodeSupply(numSources + node, -1);
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2011-03-29 13:53:49 +00:00
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}
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if (minCostFlow.solve() == MinCostFlow.Status.OPTIMAL) {
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2011-07-06 21:38:12 +00:00
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final long totalFlowCost = minCostFlow.getOptimalCost();
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System.out.println("total flow = " + totalFlowCost + "/" + expectedCost);
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for (int i = 0; i < minCostFlow.getNumArcs(); ++i) {
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if (minCostFlow.getFlow(i) > 0) {
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2019-05-06 10:31:03 +02:00
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System.out.println("From source " + minCostFlow.getTail(i) + " to target "
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+ minCostFlow.getHead(i) + ": cost " + minCostFlow.getUnitCost(i));
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}
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}
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} else {
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System.out.println("No solution found");
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}
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2011-03-29 13:53:49 +00:00
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}
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private static void solveMaxFlow() {
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System.out.println("Max Flow Problem - Simple interface");
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2011-05-26 09:33:52 +00:00
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final int[] tails = {0, 0, 0, 0, 1, 2, 3, 3, 4};
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final int[] heads = {1, 2, 3, 4, 3, 4, 4, 5, 5};
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2011-03-29 13:53:49 +00:00
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final int[] capacities = {5, 8, 5, 3, 4, 5, 6, 6, 4};
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final int expectedTotalFlow = 10;
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MaxFlow maxFlow = new MaxFlow();
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for (int i = 0; i < tails.length; ++i) {
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maxFlow.addArcWithCapacity(tails[i], heads[i], capacities[i]);
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}
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if (maxFlow.solve(0, 5) == MaxFlow.Status.OPTIMAL) {
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System.out.println("Total flow " + maxFlow.getOptimalFlow() + "/" + expectedTotalFlow);
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for (int i = 0; i < maxFlow.getNumArcs(); ++i) {
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System.out.println("From source " + maxFlow.getTail(i) + " to target " + maxFlow.getHead(i)
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+ ": " + maxFlow.getFlow(i) + " / " + maxFlow.getCapacity(i));
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2011-07-06 21:38:12 +00:00
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}
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2014-07-09 11:26:55 +00:00
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// TODO(user): Our SWIG configuration does not currently handle these
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// functions correctly in Java:
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// maxFlow.getSourceSideMinCut(...);
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// maxFlow.getSinkSideMinCut(...);
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2011-07-06 21:38:12 +00:00
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} else {
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System.out.println("There was an issue with the input.");
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2011-03-29 13:53:49 +00:00
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}
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}
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public static void main(String[] args) throws Exception {
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2020-09-11 21:17:23 +02:00
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Loader.loadNativeLibraries();
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2011-03-29 13:53:49 +00:00
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FlowExample.solveMinCostFlow();
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FlowExample.solveMaxFlow();
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}
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}
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