public KnapsackContent Solve()
{
KnapsackContent solution = new KnapsackContent();
solution = FindBetterSubOptions(solution);
return(solution);
}
public KnapsackContent(KnapsackContent currentKnapsackToCopyFrom = null)
{
if (currentKnapsackToCopyFrom != null)
{
ConsideredItems = new List <bool>(currentKnapsackToCopyFrom.ConsideredItems);
TotalValue = currentKnapsackToCopyFrom.TotalValue;
TotalWeight = currentKnapsackToCopyFrom.TotalWeight;
}
else
{
ConsideredItems = new List <bool>();
}
}
private static void SolveKnapsack()
{
Console.WriteLine("Solving your Knapsack problem..");
KnapsackSolver solver = new KnapsackSolver();
Stopwatch timer = new Stopwatch();
timer.Start();
KnapsackContent optimalSolution = solver.Solve();
timer.Stop();
Console.WriteLine($"\nOptimal solution found for Knapsack:\n{optimalSolution.Description}");
Console.WriteLine($"That took {timer.ElapsedMilliseconds:#,0}ms");
}
private KnapsackContent FindBetterSubOptions(KnapsackContent currentSack)
{
if (currentSack.ConsideredItems.Count >= _itemValues.Length)
{
return(currentSack);
}
KnapsackContent bestSolution = currentSack;
foreach (bool objectWillBeTaken in new[] { true, false }) // We consider both the cases in which we take or we leave the object where it is
{
KnapsackContent extendedSack = new KnapsackContent(currentSack);
extendedSack.ConsideredItems.Add(objectWillBeTaken); // we store the choice of taking this object or not
if (objectWillBeTaken) // if we take it..
{
extendedSack.TotalWeight += _itemWeights[extendedSack.ConsideredItems.Count - 1]; // we add the weight:
if (!extendedSack.IsValid) // if this makes our knapsack explode, we'll ignore this combination
{
continue;
}
extendedSack.TotalValue += _itemValues[extendedSack.ConsideredItems.Count - 1]; // otherwise we also add its value
}
extendedSack = FindBetterSubOptions(extendedSack); // we then check the best solution we can have among all the objects we still have to evaluate
if ((bestSolution != currentSack) && (bestSolution.TotalValue >= extendedSack.TotalValue)) // If we already have a better solution for this initial combination
{
continue; // ...we discard it...
}
bestSolution = extendedSack; // ...otherwise, it will become our current best local solution.
}
Console.Write(".");
return(bestSolution);
}
