private int GetEstimatedValue(KnapsackItem[] ksItems)
{
var collectedWeight = 0;
var estimatedValue = 0;
var itemsByRatio = ksItems.OrderByDescending(k => Convert.ToDouble(k.Value) / Convert.ToDouble(k.Weight));
foreach (var item in ksItems) item.EstimatedValue = item.Value;
foreach (var item in itemsByRatio)
{
if (collectedWeight + item.Weight <= _capacity)
{
collectedWeight += item.Weight;
estimatedValue += item.Value;
if (collectedWeight == _capacity) break;
}
else
{
var percentOfItem = (_capacity - collectedWeight) / Convert.ToDouble(item.Weight);
var partialValue = Convert.ToInt32(percentOfItem*item.Value);
estimatedValue += partialValue;
item.EstimatedValue = partialValue;
break;
}
}
return estimatedValue;
}
private void BuildTree(KnapsackNode node, KnapsackItem[] ksItems)
{
//if possible add contents of next ksitem to node
// if so recruse with remaining items
// if not determine if best and set if so
//also, recurse with unchanged node items and remaining items
if (ksItems.Length == 0) return;
var item = ksItems.First();
var newValue = node.AccumulatedValue + item.Value;
var newWeight = node.AccumulatedWeight + item.Weight;
var remainingCapacity = _capacity - newWeight;
var rest = ksItems.Skip(1).ToArray();
//if i was able to add something
if (remainingCapacity >= 0)
{
var newNode = new KnapsackNode(newValue, newWeight);
newNode.SelectedItems.AddRange(node.SelectedItems);
newNode.SelectedItems.Add(item.Id);
if (remainingCapacity > 0) BuildTree(newNode, rest);
if (newNode.AccumulatedValue > _bestNode.AccumulatedValue) _bestNode = newNode;
}
//this is to use first node but not adding current item
if (rest.Any(k => k.Weight + node.AccumulatedWeight <= _capacity) && (rest.Sum(k => k.Value) + node.AccumulatedValue) > _bestNode.AccumulatedValue)
{
BuildTree(node, rest);
}
}
public void Execute(int capacity, KnapsackItem[] ksItems)
{
_capacity = capacity;
for (var i = 0; i < ksItems.Length; i++)
{
var itemsToProcess = ksItems.Skip(i).ToArray();
var estimatedValue = GetEstimatedValue(itemsToProcess);
var firstItem = itemsToProcess.First();
var firstNode = new KnapsackNode(firstItem.Value, firstItem.Weight, estimatedValue);
firstNode.SelectedItems.Add(firstItem.Id);
if (_bestNode == null) _bestNode = firstNode;
if (estimatedValue <= _bestNode.AccumulatedValue) continue;
var remaining = itemsToProcess.Skip(1).ToArray();
BuildTree(firstNode, remaining);
}
foreach (var i in _bestNode.SelectedItems)
{
var ksItem = ksItems.Single(p => p.Id == i);
ksItem.Selected = 1;
}
}
public void Execute(int capacity, KnapsackItem[] ksItems)
{
var collectedWeight = 0;
var itemsToUpdate = ksItems.OrderByDescending(k => Convert.ToDouble(k.Value) / Convert.ToDouble(k.Weight))
.ToArray();
foreach (var itemToUpdate in itemsToUpdate)
{
if (itemToUpdate.Weight + collectedWeight <= capacity)
{
collectedWeight += itemToUpdate.Weight;
itemToUpdate.Selected = 1;
}
if (collectedWeight == capacity) break;
}
}
public void Execute(int capacity, KnapsackItem[] ksItems)
{
_bestNode = new KnapsackNode(0, 0);
_capacity = capacity;
for (var i = 0; i < ksItems.Length; i++)
{
var itemsToProcess = ksItems.Skip(i).ToArray();
var firstItem = itemsToProcess.First();
var firstNode = new KnapsackNode(firstItem.Value, firstItem.Weight);
firstNode.SelectedItems.Add(firstItem.Id);
var remaining = itemsToProcess.Skip(1).ToArray();
BuildTree(firstNode, remaining);
}
foreach (var i in _bestNode.SelectedItems)
{
var ksItem = ksItems.Single(p => p.Id == i);
ksItem.Selected = 1;
}
}