75 lines
2.6 KiB
Java
75 lines
2.6 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.MaxFlow;
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import java.util.ArrayList;
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import java.util.List;
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// [END import]
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/** Minimal MaxFlow program.*/
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public final class SimpleMaxFlowProgram {
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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 SimpleMaxFlow solver.
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MaxFlow maxFlow = new MaxFlow();
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// [END solver]
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// [START data]
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// Define three parallel arrays: start_nodes, end_nodes, and the capacities
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// between each pair. For instance, the arc from node 0 to node 1 has a
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// capacity of 20.
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// From Taha's 'Introduction to Operations Research',
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// example 6.4-2.
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int[] startNodes = new int[] {0, 0, 0, 1, 1, 2, 2, 3, 3};
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int[] endNodes = new int[] {1, 2, 3, 2, 4, 3, 4, 2, 4};
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int[] capacities = new int[] {20, 30, 10, 40, 30, 10, 20, 5, 20};
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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 = maxFlow.addArcWithCapacity(startNodes[i], endNodes[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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// [END constraints]
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// [START solve]
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// Find the maximum flow between node 0 and node 4.
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MaxFlow.Status status = maxFlow.solve(0, 4);
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// [END solve]
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// [START print_solution]
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if (status == MaxFlow.Status.OPTIMAL) {
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System.out.println("Max. flow: " + maxFlow.getOptimalFlow());
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System.out.println("");
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System.out.println(" Arc Flow / Capacity");
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for (int i = 0; i < maxFlow.getNumArcs(); ++i) {
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System.out.println(maxFlow.getTail(i) + " -> " + maxFlow.getHead(i) + " "
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+ maxFlow.getFlow(i) + " / " + maxFlow.getCapacity(i));
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}
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} else {
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System.out.println("Solving the max flow problem failed. Solver status: " + status);
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}
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// [END print_solution]
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}
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private SimpleMaxFlowProgram() {}
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}
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// [END program]
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