dotnet: Add FlowTests.cs (Fix #3482)

* expose missing MaxFlow::SetArcCapacity()

ortools/graph/csharp/FlowTests.cs

@@ -0,0 +1,83 @@
+// Copyright 2010-2022 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using Xunit;
+using Google.OrTools.Graph;
+
+namespace Google.OrTools.Tests
+{
+public class FlowTest
+{
+    [Fact]
+    public void testMinCostFlow()
+    {
+        int numSources = 4;
+        int numTargets = 4;
+        int[,] costs = { { 90, 75, 75, 80 }, { 35, 85, 55, 65 }, { 125, 95, 90, 105 }, { 45, 110, 95, 115 } };
+        int expectedCost = 275;
+        MinCostFlow minCostFlow = new MinCostFlow();
+        Assert.NotNull(minCostFlow);
+        for (int source = 0; source < numSources; ++source)
+        {
+            for (int target = 0; target < numTargets; ++target)
+            {
+                minCostFlow.AddArcWithCapacityAndUnitCost(source, numSources + target, 1, costs[source, target]);
+            }
+        }
+
+        for (int source = 0; source < numSources; ++source)
+        {
+            minCostFlow.SetNodeSupply(source, 1);
+        }
+        for (int target = 0; target < numTargets; ++target)
+        {
+            minCostFlow.SetNodeSupply(numSources + target, -1);
+        }
+        MinCostFlowBase.Status solveStatus = minCostFlow.Solve();
+        Assert.Equal(solveStatus, MinCostFlow.Status.OPTIMAL);
+        long totalFlowCost = minCostFlow.OptimalCost();
+        Assert.Equal(expectedCost, totalFlowCost);
+    }
+
+    [Fact]
+    public void testMaxFlow()
+    {
+        int numNodes = 6;
+        int numArcs = 9;
+        int[] tails = { 0, 0, 0, 0, 1, 2, 3, 3, 4 };
+        int[] heads = { 1, 2, 3, 4, 3, 4, 4, 5, 5 };
+        int[] capacities = { 5, 8, 2, 0, 4, 5, 6, 0, 4 };
+        int[] expectedFlows = { 4, 4, 2, 0, 4, 4, 0, 6, 4 };
+        int expectedTotalFlow = 10;
+        MaxFlow maxFlow = new MaxFlow();
+        Assert.NotNull(maxFlow);
+        for (int i = 0; i < numArcs; ++i)
+        {
+            maxFlow.AddArcWithCapacity(tails[i], heads[i], capacities[i]);
+        }
+        maxFlow.SetArcCapacity(7, 6);
+        MaxFlow.Status solveStatus = maxFlow.Solve(/*source=*/0, /*sink=*/numNodes - 1);
+        Assert.Equal(solveStatus, MaxFlow.Status.OPTIMAL);
+
+        long totalFlow = maxFlow.OptimalFlow();
+        Assert.Equal(expectedTotalFlow, totalFlow);
+
+        Assert.Equal(numArcs, maxFlow.NumArcs());
+        for (int i = 0; i < numArcs; ++i)
+        {
+            Assert.Equal(maxFlow.Flow(i), expectedFlows[i]);
+        }
+    }
+}
+} // namespace Google.OrTools.Tests

ortools/graph/csharp/graph.i

@@ -46,6 +46,7 @@
 %unignore operations_research::SimpleMaxFlow::SimpleMaxFlow;
 %unignore operations_research::SimpleMaxFlow::~SimpleMaxFlow;
 %unignore operations_research::SimpleMaxFlow::AddArcWithCapacity;
+%unignore operations_research::SimpleMaxFlow::SetArcCapacity;
 %unignore operations_research::SimpleMaxFlow::Solve;
 %unignore operations_research::SimpleMaxFlow::NumNodes;
 %unignore operations_research::SimpleMaxFlow::NumArcs;