text: // Copyright 2010-2021 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.
  
  #include <cstdlib>
  
  #include "ortools/base/init_google.h"
  #include "ortools/base/logging.h"
  #include "ortools/graph/ebert_graph.h"
  #include "ortools/graph/linear_assignment.h"
  
  namespace operations_research {
  
  // Test assignment on a 4x4 matrix. Example taken from
  // http://www.ee.oulu.fi/~mpa/matreng/eem1_2-1.htm with kCost[0][1]
  // modified so the optimum solution is unique.
  void AssignmentOn4x4Matrix() {
    LOG(INFO) << "Assignment on 4x4 Matrix";
    const int kNumSources = 4;
    const int kNumTargets = 4;
    const CostValue kCost[kNumSources][kNumTargets] = {{90, 76, 75, 80},
                                                       {35, 85, 55, 65},
                                                       {125, 95, 90, 105},
                                                       {45, 110, 95, 115}};
    const CostValue kExpectedCost =
        kCost[0][3] + kCost[1][2] + kCost[2][1] + kCost[3][0];
    ForwardStarGraph graph(kNumSources + kNumTargets, kNumSources * kNumTargets);
    LinearSumAssignment<ForwardStarGraph> assignment(graph, kNumSources);
    for (NodeIndex source = 0; source < kNumSources; ++source) {
      for (NodeIndex target = 0; target < kNumTargets; ++target) {
        ArcIndex arc = graph.AddArc(source, kNumSources + target);
        assignment.SetArcCost(arc, kCost[source][target]);
      }
    }
    CHECK(assignment.ComputeAssignment());
    CostValue total_cost = assignment.GetCost();
    CHECK_EQ(kExpectedCost, total_cost);
  }
  
  void AnotherAssignment() {
    LOG(INFO) << "Another assignment on 4x4 matrix";
    std::vector<std::vector<int>> matrice(
        {{8, 7, 9, 9}, {5, 2, 7, 8}, {6, 1, 4, 9}, {2, 3, 2, 6}});
    const int kSize = matrice.size();
    ForwardStarGraph graph(2 * kSize, kSize * kSize);
    LinearSumAssignment<ForwardStarGraph> assignement(graph, kSize);
    for (int i = 0; i < kSize; ++i) {
      CHECK_EQ(kSize, matrice[i].size());
      for (int j = 0; j < kSize; ++j) {
        int arcIndex = graph.AddArc(i, j + kSize);
        assignement.SetArcCost(arcIndex, matrice[i][j]);
      }
    }
  
    assignement.ComputeAssignment();
    LOG(INFO) << "Cost : " << assignement.GetCost();
  }
  
  }  // namespace operations_research
  
  int main(int argc, char** argv) {
    InitGoogle(argv[0], &argc, &argv, true);
    operations_research::AssignmentOn4x4Matrix();
    operations_research::AnotherAssignment();
    return EXIT_SUCCESS;
  }
  