course_scheduling.h

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// Copyright 2010-2025 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.
 
#ifndef ORTOOLS_SCHEDULING_COURSE_SCHEDULING_H_
#define ORTOOLS_SCHEDULING_COURSE_SCHEDULING_H_
 
#include <utility>
#include <vector>
 
#include "absl/container/flat_hash_set.h"
#include "absl/status/status.h"
#include "absl/types/span.h"
#include "ortools/linear_solver/linear_solver.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/scheduling/course_scheduling.pb.h"
 
namespace operations_research {
class CourseSchedulingSolver {
 public:
  CourseSchedulingSolver() : solve_for_rooms_(false) {}
  virtual ~CourseSchedulingSolver() = default;
 
  using ConflictPairs = absl::flat_hash_set<std::pair<int, int>>;
 
  CourseSchedulingResult Solve(const CourseSchedulingModel& model);
 
 protected:
  virtual absl::Status ValidateModelAndLoadClasses(
      const CourseSchedulingModel& model);
 
  virtual CourseSchedulingResult SolveModel(
      const CourseSchedulingModel& model, const ConflictPairs& class_conflicts);
 
  virtual absl::Status VerifyCourseSchedulingResult(
      const CourseSchedulingModel& model, const CourseSchedulingResult& result);
 
 private:
  CourseSchedulingResult ScheduleCourses(const ConflictPairs& class_conflicts,
                                         const CourseSchedulingModel& model);
 
  // This method will modify the CourseSchedulingResult returned from
  // ScheduleCoursesMip, which is why the result is passed in as a pointer.
  ConflictPairs AssignStudents(const CourseSchedulingModel& model,
                               CourseSchedulingResult* result);
 
  int GetTeacherIndex(int course_index, int section);
 
  void InsertSortedPairs(absl::Span<const int> list, ConflictPairs* pairs);
 
  bool ShouldCreateVariable(int course_index, int section, int time_slot,
                            int room);
 
  std::vector<int> GetRoomIndices(const Course& course);
 
  std::vector<absl::flat_hash_set<int>> GetClassesByTimeSlot(
      const CourseSchedulingResult* result);
 
  void AddVariableIfNonNull(double coeff, const MPVariable* var,
                            MPConstraint* ct);
 
  CourseSchedulingResultStatus MipStatusToCourseSchedulingResultStatus(
      MPSolver::ResultStatus mip_status);
 
  bool solve_for_rooms_;
  int class_count_;
  int time_slot_count_;
  int room_count_;
  ConflictPairs course_conflicts_;
  std::vector<absl::flat_hash_set<int>> teacher_to_classes_;
  std::vector<absl::flat_hash_set<int>> teacher_to_restricted_slots_;
  std::vector<std::vector<int>> course_to_classes_;
};
 
}  // namespace operations_research
 
#endif  // ORTOOLS_SCHEDULING_COURSE_SCHEDULING_H_