/**
* Calculates the value/cost ratio for each object
* And stores the ratios in a vector
* TODO sort values to improve runtime
* @param k the knapsack to use
*/
void calculateValueCostRatios(knapsack &k) {
for (int i = 0; i < k.getNumObjects(); i++)
{
valueCostRatio.insert(valueCostRatio.begin() + i,
(k.getValue(i) / (double)k.getCost(i)));
}
}
knapsack::knapsack(const knapsack &k)
// Knapsack copy constructor
{
numObjects = k.getNumObjects();
costBound = k.getCostBound();
value.resize(numObjects);
cost.resize(numObjects);
index.resize(numObjects);
selected.resize(numObjects);
for (int i = 0; i < numObjects; i++)
{
setValue(i,k.getValue(i));
setCost(i,k.getCost(i));
setIndex(i,k.getIndex(i));
if (k.isSelected(i))
select(i);
else
unSelect(i);
}
setNum(k.getNum());
currentValue = k.getCurrentValue();
currentCost = k.getCurrentCost();
}
knapsack greedyKnapsack(vector<pair<double,int>> sortedSack, knapsack sack)
{
int sackIndex;
// outer for loop is iterating through sortedSack ratios
// look for highest ratio item
for (int i = 0; i < sack.getNumObjects(); i++)
{
// use second value of sorted sack pair as index
sackIndex = sortedSack.at(i).second;
//get ratio for specific sack(sackIndex)
double ratioKnap;
double valKnap = sack.getValue(sackIndex);
double costKnap = sack.getCost(sackIndex);
ratioKnap = valKnap / costKnap;
if (sack.getCost() + sack.getCost(sackIndex) <= sack.getCostLimit())
{
sack.select(sackIndex);
}
}
for (int k = 0; k < sack.getNumObjects(); k++)
{
cout<<sack.isSelected(k)<<endl;
}
return sack;
}
double greedyKnapsack(knapsack &k){
MaxHeap<float, int>* heap = new MaxHeap<float, int>(&compare);
for(int counter = 0; counter < k.getNumObjects(); counter++){
double key = (double) k.getValue(counter) / k.getCost(counter);
heap->add(key, counter);
}
while(! heap->empty()){
int next = heap->extractMaxHeapMaximum();
if(k.getCost(next) + k.getCurrentCost() <= k.getCostBound()){
k.select(next);
}
}
return k.getCurrentValue();
}
void printSolution(knapsack &k, string filename)
// Prints out the solution.
{
ofstream myfile;
myfile.open (filename.c_str());
myfile << "------------------------------------------------" << endl;
myfile << "Total value: " << k.getCurrentValue() << endl;
myfile << "Total cost: " << k.getCurrentCost() << endl << endl;
// Print out objects in the solution
for (int i = 0; i < k.getNumObjects(); i++)
if (k.isSelected(i))
myfile << i << " " << k.getValue(i) << " " << k.getCost(i) << endl;
myfile << endl;
myfile.close();
}
// sort all items in order of value/weight ratio
// and store the ratios in the index at which they exist in knapsack
vector<pair<double, int>> sortItems(knapsack sack)
{
vector<pair<double, int>> ratios;
for (int i = 0; i < sack.getNumObjects(); i++)
{
//cout << "sack.getValue(" << i << ")" << " = " << sack.getValue(i) << endl;
//cout << "sack.getValue(" << i << ")" << " = " << sack.getCost(i) << endl;
double ratio;
double val = sack.getValue(i);
double cost = sack.getCost(i);
ratio = val / cost;
//cout << "Ratio: " << ratio;
//cout << "Pushing " << ratio << " to index " << i << endl;
pair <double, int> ratInd; // ratio + index
ratInd.first = ratio;
ratInd.second = i;
ratios.push_back(ratInd);
//cout << endl << endl << endl;
}
// this preserves the original ratios vector just in case (may remove it later)
vector<pair<double,int>> sortedRatios = ratios;
sort(sortedRatios.begin(), sortedRatios.end());
reverse(sortedRatios.begin(), sortedRatios.end());
/*
for (int i = 0; i < ratios.size(); i++)
{
//cout << "Ratio: " << sortedRatios.at(i) << " at index " << i << endl;
//cout << "" << sortedRatios.at(i) << endl;
}*/
cin.get();
return sortedRatios;
}
