public static Solution RandomFeasibleSolution(VrptwProblem problem)
{
Solution solution = new Solution(problem);
var customersToAssign = new List <Customer>(problem.Customers);
while (customersToAssign.Count != 0)
{
Route route = new Route(problem);
route.AddCustomer(problem.Depot);
while (true)
{
float totalTime = route.TotalTime();
Customer lastOneInRoute = route.Customers.Last();
var feasibleCustomers = customersToAssign.Where(
c =>
c.ReadyTime >= totalTime + problem.GetDistance(c.Id, lastOneInRoute.Id) ||
(c.ReadyTime < totalTime + problem.GetDistance(c.Id, lastOneInRoute.Id) &&
c.DueDate >= totalTime + problem.GetDistance(c.Id, lastOneInRoute.Id))).ToList();
if (feasibleCustomers.Count > 0)
{
Customer randomCustomer = feasibleCustomers.ElementAt(RandomGenerator.NextInt(feasibleCustomers.Count()));
customersToAssign.Remove(randomCustomer);
route.AddCustomer(randomCustomer);
}
else
{
route.AddCustomer(problem.Depot);
solution.Routes.Add(route);
break;
}
}
}
return(solution);
}
/// <summary>
/// Creates a new feasible solution chosen randomly from the neighbourbood
/// of the <param name="solution">solution</param>.
/// </summary>
/// <param name="solution">The solution.</param>
/// <returns></returns>
public static Solution FeasibleNeighbourSolution(Solution solution)
{
Solution newSolution = (Solution)solution.Clone();
bool isSolutionFeasible;
do
{
int routeToTakeFromIndex, routeToGiveToIndex;
RandomGenerator.NextTwoDifferentInts(newSolution.Routes.Count, out routeToTakeFromIndex, out routeToGiveToIndex);
Route routeToTakeFrom = newSolution.Routes.ElementAt(routeToTakeFromIndex);
Route routeToGiveTo = newSolution.Routes.ElementAt(routeToGiveToIndex);
// backup copies in the case the solution was infeasible
Route routeToTakeFromCopy = (Route)routeToTakeFrom.Clone();
Route routeToGiveToCopy = (Route)routeToGiveTo.Clone();
// move customer to another route
int customerToMoveIndex = RandomGenerator.NextInt(routeToTakeFrom.Customers.Count - 2) + 1;
var customerToMove = routeToTakeFrom.Customers.ElementAt(customerToMoveIndex);
routeToTakeFrom.RemoveCustomer(customerToMove);
int placeToMoveCustomer = RandomGenerator.NextInt(routeToGiveTo.Customers.Count - 2) + 1;
routeToGiveTo.AddCustomer(customerToMove, placeToMoveCustomer);
isSolutionFeasible = newSolution.IsFeasible();
// if new solution sint feasible, bring back saved routes
if (!isSolutionFeasible)
{
newSolution.Routes[routeToTakeFromIndex] = routeToTakeFromCopy;
newSolution.Routes[routeToGiveToIndex] = routeToGiveToCopy;
}
// if route is empty, remove it from the solution
else if (routeToTakeFrom.IsEmpty())
{
newSolution.Routes.Remove(routeToTakeFrom);
}
} while (!isSolutionFeasible);
return(newSolution);
}
