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Core/Calculation/TeamScheduler.cs

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+using Core.Entities;
+using Google.OrTools.Sat;
+
+namespace Core.Calculation;
+public class TeamScheduler
+{
+	private readonly IList<Student> _studentObjs;
+	private readonly IList<Team> _teamObjs;
+
+	private readonly int[] _students;
+	private readonly int[] _teams;
+	private readonly int[] _timeSlots;
+
+	private readonly List<Tuple<int,int>> _scheduleSeparateTeams = new ();
+
+	public TeamScheduler(IList<Team>  teams, int numTimeSlots)
+	{
+		_teamObjs = teams;
+		_studentObjs = teams.SelectMany(t => t.Students).Distinct().ToList();
+
+		_students = Enumerable.Range(0, _studentObjs.Count).ToArray();
+		_teams = Enumerable.Range(0, _teamObjs.Count).ToArray();
+		_timeSlots = Enumerable.Range(0, numTimeSlots).ToArray();
+	}
+
+	public void ScheduleSeparate(Team team1, Team team2)
+	{
+		var one = _teamObjs.IndexOf(team1);
+		var two = _teamObjs.IndexOf(team2);
+		_scheduleSeparateTeams.Add(Tuple.Create(one,two));
+	}
+
+	public static TeamScheduler CreateInstance(IList<Team> teams, int numTimeSlots)
+	{
+		return new TeamScheduler(teams, numTimeSlots);
+	}
+
+	public IList<Team>[] Solve()
+	{
+		// Model.
+		var model = new CpModel();
+
+		// Data
+		var m = new int[_students.Length,_teams.Length];
+		foreach (var i in _students)
+		foreach (var t in _teams)
+			m[i, t] = _studentObjs[i].Teams.Contains(_teamObjs[t]) ? 1 : 0;
+
+		// Variables.
+		// x - 1 if meeting of team t takes place at time slot s, else 0
+		var x = new IntVar[_teams.Length, _timeSlots.Length];
+		foreach (var t in _teams)
+		foreach (var s in _timeSlots)
+			x[t, s] = model.NewIntVar(0, 1,$"team time slots[{t},{s}]");
+
+		// y - 1 if individual i has meetings at time slot s, 0 otherwise
+		var y = new IntVar[_students.Length, _timeSlots.Length];
+		foreach (var i in _students)
+		foreach (var s in _timeSlots)
+			y[i, s] = model.NewIntVar(0, 1, $"individual time slots[{i},{s}]");
+
+		// each team meets exactly one time
+		foreach (var t in _teams)
+			model.AddLinearConstraint(LinearExpr.Sum(_timeSlots.Select(s => x[t, s])), 1L, 1L);
+		
+		// individual must have at least one team meeting at the given time slot to attend
+		foreach (var i in _students)
+		foreach (var s in _timeSlots)
+			model.Add(
+				new BoundedLinearExpression(
+					y[i, s],
+					LinearExpr.Sum(_teams.Select(t => m[i, t] * x[t, s])),
+					false));
+
+		// maximize number of times individuals meet
+		var indTimeSlotVars = LinearExpr.NewBuilder();
+		foreach (var i in _students)
+		foreach (var s in _timeSlots)
+			indTimeSlotVars.Add(y[i, s]);
+		model.Minimize(indTimeSlotVars);
+
+		foreach (var ts in _scheduleSeparateTeams)
+		foreach (var s in _timeSlots)
+			model.Add(x[ts.Item1, s] != x[ts.Item2, s]);
+			//model.Add(
+			//	new BoundedLinearExpression(
+			//		x[ts.Item1, s],
+			//		x[ts.Item2, s],
+			//		false));
+
+		var solver = new CpSolver();
+		
+		var cpSolverStatus = solver.Solve(model);
+		Console.WriteLine($"Solver status: {cpSolverStatus}");
+
+		if (cpSolverStatus is CpSolverStatus.Optimal or CpSolverStatus.Feasible)
+		{
+			Console.WriteLine($"Total cost: {solver.ObjectiveValue}\n");
+
+			//foreach (var t in _teams)
+			//foreach (var s in _timeSlots)
+			//{
+			//	if (solver.Value(x[t, s]) > 0)
+			//		Console.WriteLine($"{_teamObjs[t].Name} : {s}");
+			//}
+
+			//foreach (var i in _students)
+			//foreach (var s in _timeSlots)
+			//{
+			//	if (solver.Value(y[i, s]) > 0)
+			//		Console.WriteLine($"{_studentObjs[i].Name} : {s}");
+			//}
+
+			var timeSlotTeams = new List<Team>[_timeSlots.Length];
+			foreach (var s in _timeSlots)
+			{
+				var teams = new List<Team>();
+				foreach (var t in _teams)
+				{
+					if (solver.Value(x[t, s]) > 0)
+					{
+						teams.Add(_teamObjs[t]); 
+					}
+				}
+				timeSlotTeams[s] = teams;
+			}
+			return timeSlotTeams;
+		}
+		else
+		{
+			//Console.WriteLine("No solution found.");
+			return Array.Empty<IList<Team>>();
+		}
+
+	}
+}