knapsack.cc

// Copyright 2018 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.

// Bi-dimensional knapsack problem.

#include <iterator>
#include <numeric>
#include <sstream>
#include "ortools/algorithms/knapsack_solver.h"
#include "ortools/base/logging.h"

namespace operations_research {
void RunKnapsackExample() {
  // Instantiate the solver.
  KnapsackSolver solver(
      KnapsackSolver::KNAPSACK_MULTIDIMENSION_BRANCH_AND_BOUND_SOLVER,
      "KnapsackExample");

  std::vector<int64> values = {
      360, 83, 59,  130, 431, 67, 230, 52,  93,  125, 670, 892, 600,
      38,  48, 147, 78,  256, 63, 17,  120, 164, 432, 35,  92,  110,
      22,  42, 50,  323, 514, 28, 87,  73,  78,  15,  26,  78,  210,
      36,  85, 189, 274, 43,  33, 10,  19,  389, 276, 312};

  std::vector<std::vector<int64>> weights = {
      {7,  0,  30, 22, 80, 94, 11, 81, 70, 64, 59, 18, 0,  36, 3,  8,  15,
       42, 9,  0,  42, 47, 52, 32, 26, 48, 55, 6,  29, 84, 2,  4,  18, 56,
       7,  29, 93, 44, 71, 3,  86, 66, 31, 65, 0,  79, 20, 65, 52, 13}};

  std::vector<int64> capacities = {850};

  solver.Init(values, weights, capacities);
  int64 computed_value = solver.Solve();

  // Print solution
  std::vector<int> packed_items;
  for (std::size_t i = 0; i < values.size(); ++i) {
    if (solver.BestSolutionContains(i)) packed_items.push_back(i);
  }
  std::ostringstream packed_items_ss;
  std::copy(packed_items.begin(), packed_items.end() - 1,
            std::ostream_iterator<int>(packed_items_ss, ", "));
  packed_items_ss << packed_items.back();

  std::vector<int64> packed_weights;
  packed_weights.reserve(packed_items.size());
  for (const auto &it : packed_items) {
    packed_weights.push_back(weights[0][it]);
  }
  std::ostringstream packed_weights_ss;
  std::copy(packed_weights.begin(), packed_weights.end() - 1,
            std::ostream_iterator<int>(packed_weights_ss, ", "));
  packed_weights_ss << packed_weights.back();

  int64 total_weights =
      std::accumulate(packed_weights.begin(), packed_weights.end(), 0LL);

  LOG(INFO) << "Total value: " << computed_value;
  LOG(INFO) << "Packed items: {" << packed_items_ss.str() << "}";
  LOG(INFO) << "Total weight: " << total_weights;
  LOG(INFO) << "Packed weights: {" << packed_weights_ss.str() << "}";
}
}  // namespace operations_research

int main(int argc, char **argv) {
  google::InitGoogleLogging(argv[0]);
  FLAGS_logtostderr = 1;
  operations_research::RunKnapsackExample();
  return EXIT_SUCCESS;
}