97 lines
3.7 KiB
Java
97 lines
3.7 KiB
Java
// Copyright 2010-2021 Google LLC
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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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// [START program]
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package com.google.ortools.graph.samples;
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// [START import]
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import com.google.ortools.Loader;
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import com.google.ortools.graph.MinCostFlow;
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import com.google.ortools.graph.MinCostFlowBase;
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// [END import]
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/** Minimal Assignment Min Flow. */
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public class BalanceMinFlow {
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public static void main(String[] args) throws Exception {
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Loader.loadNativeLibraries();
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// [START solver]
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// Instantiate a SimpleMinCostFlow solver.
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MinCostFlow minCostFlow = new MinCostFlow();
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// [END solver]
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// [START data]
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// Define the directed graph for the flow.
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// int[] teamA = new int[] {1, 3, 5};
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// int[] teamB = new int[] {2, 4, 6};
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int[] startNodes = new int[] {0, 0, 11, 11, 11, 12, 12, 12, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3,
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4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 8, 9, 10};
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int[] endNodes = new int[] {11, 12, 1, 3, 5, 2, 4, 6, 7, 8, 9, 10, 7, 8, 9, 10, 7, 8, 9, 10, 7,
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8, 9, 10, 7, 8, 9, 10, 7, 8, 9, 10, 13, 13, 13, 13};
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int[] capacities = new int[] {2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
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int[] unitCosts = new int[] {0, 0, 0, 0, 0, 0, 0, 0, 90, 76, 75, 70, 35, 85, 55, 65, 125, 95,
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90, 105, 45, 110, 95, 115, 60, 105, 80, 75, 45, 65, 110, 95, 0, 0, 0, 0};
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int tasks = 4;
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// Define an array of supplies at each node.
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int[] supplies = new int[] {tasks, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -tasks};
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// [END data]
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// [START constraints]
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// Add each arc.
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for (int i = 0; i < startNodes.length; ++i) {
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int arc = minCostFlow.addArcWithCapacityAndUnitCost(
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startNodes[i], endNodes[i], capacities[i], unitCosts[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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}
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// Add node supplies.
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for (int i = 0; i < supplies.length; ++i) {
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minCostFlow.setNodeSupply(i, supplies[i]);
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}
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// [END constraints]
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// [START solve]
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// Find the min cost flow.
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MinCostFlowBase.Status status = minCostFlow.solve();
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// [END solve]
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// [START print_solution]
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if (status == MinCostFlow.Status.OPTIMAL) {
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System.out.println("Total cost: " + minCostFlow.getOptimalCost());
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System.out.println();
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for (int i = 0; i < minCostFlow.getNumArcs(); ++i) {
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// Can ignore arcs leading out of source or intermediate nodes, or into sink.
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if (minCostFlow.getTail(i) != 0 && minCostFlow.getTail(i) != 11
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&& minCostFlow.getTail(i) != 12 && minCostFlow.getHead(i) != 13) {
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// Arcs in the solution have a flow value of 1. Their start and end nodes
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// give an assignment of worker to task.
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if (minCostFlow.getFlow(i) > 0) {
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System.out.println("Worker " + minCostFlow.getTail(i) + " assigned to task "
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+ minCostFlow.getHead(i) + " Cost: " + minCostFlow.getUnitCost(i));
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}
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}
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}
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} else {
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System.out.println("Solving the min cost flow problem failed.");
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System.out.println("Solver status: " + status);
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}
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// [END print_solution]
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}
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private BalanceMinFlow() {}
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}
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// [END program]
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