91 lines
3.2 KiB
Java
91 lines
3.2 KiB
Java
// Copyright 2010 Google
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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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package com.google.ortools.flow.samples;
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import com.google.ortools.flow.MaxFlow;
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import com.google.ortools.flow.MinCostFlow;
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import com.google.ortools.flow.StarGraph;
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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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*/
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public class FlowExample {
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static {
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System.loadLibrary("jniflow");
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}
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private static void solveMinCostFlow() {
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System.out.println("Min Cost Flow Problem");
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final int numSources = 4;
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final int numTargets = 4;
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final int[][] costs = {{90, 75, 75, 80},
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{35, 85, 55, 65},
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{125, 95, 90, 105},
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{45, 110, 95, 115}};
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final int expectedCost = 275;
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StarGraph graph = new StarGraph(numSources + numTargets,
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numSources * numTargets);
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MinCostFlow minCostFlow = new MinCostFlow(graph);
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for (int source = 1; source <= numSources; ++source) {
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for (int target = 1; target <= numTargets; ++target) {
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final long arc = graph.addArc(source, numSources + target);
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minCostFlow.setArcUnitCost(arc, costs[source - 1][target - 1]);
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minCostFlow.setArcCapacity(arc, 1);
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}
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}
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for (int source = 1; source <= numSources; ++source) {
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minCostFlow.setNodeSupply(source, 1);
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}
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for (int target = 1; target <= numTargets; ++target) {
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minCostFlow.setNodeSupply(numSources + target, -1);
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}
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final long totalFlowCost = minCostFlow.computeMinCostFlow();
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System.out.println("total flow = " + totalFlowCost + "/" + expectedCost);
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}
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private static void solveMaxFlow() {
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System.out.println("Max Flow Problem");
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final int numNodes = 6;
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final int numArcs = 9;
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final int[] tails = {1, 1, 1, 1, 2, 3, 4, 4, 5};
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final int[] heads = {2, 3, 4, 5, 4, 5, 5, 6, 6};
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final int[] capacities = {5, 8, 5, 3, 4, 5, 6, 6, 4};
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final int[] expectedFlows = {4, 4, 2, 0, 4, 4, 0, 6, 4};
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final int expectedTotalFlow = 10;
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StarGraph graph = new StarGraph(numNodes, numArcs);
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MaxFlow maxFlow = new MaxFlow(graph, 1, numNodes);
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for (int i = 0; i < numArcs; ++i) {
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final long arc = graph.addArc(tails[i], heads[i]);
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maxFlow.setArcCapacity(arc, capacities[i]);
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}
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final long totalFlow = maxFlow.computeMaxFlow();
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System.out.println("total flow " + totalFlow + "/" + expectedTotalFlow);
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for (int i = 0; i < numArcs; ++i) {
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System.out.println("Arc " + i + ": " + maxFlow.flow(i + 1) + "/" +
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expectedFlows[i]);
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}
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}
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public static void main(String[] args) throws Exception {
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FlowExample.solveMinCostFlow();
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FlowExample.solveMaxFlow();
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}
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}
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