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;
}
/**
* Uses a greedy algorithm to find the best solution
* @param k the knapsack to use
* @param t the time limit
*/
void greedySolve(knapsack &k)
{
calculateValueCostRatios(k);
while (k.getCost() < k.getCostLimit()) {
checkTimeLimit();
int best = getBestObject(k);
if (best == -1)
break;
k.select(best);
valueCostRatio[best] = 0;
}
}
/**
* @param k knapsack to find a solution for
* @return new knapsack with a random solution
*/
knapsack randomSolution(knapsack &k)
{
int i = 0;
while (checkValid(k) && i < k.getNumObjects())
{
int random = rand() % 2;
if (random == 1 && (k.getCost() + k.getCost(i)) < k.getCostLimit())
k.select(i);
else
k.unSelect(i);
i++;
}
return k;
}
/**
* Selects the current best object to select
* @param k the knapsack to use
*/
int getBestObject(knapsack &k) {
int best = -1;
for (int i = 0; i < k.getNumObjects(); i++)
{
if (best == -1 || valueCostRatio[i] > valueCostRatio[best])
{
if (valueCostRatio[i] > 0 && k.getCost(i) <= (k.getCostLimit() - k.getCost()))
{
best = i;
}
}
}
return best;
}
void exhaustiveKnapsack(knapsack sack, int timeLimit)
{
// Get start time to be used in while loop
time_t startTime;
time(&startTime);
// a while loop that expires when time limit is complete by checking difference of
// start time and current time at every loop
while (true)
{
// Get current time and stop when greater than input time limit
time_t newTime;
time(&newTime);
if (difftime(newTime, startTime) > timeLimit)
{
cout << "Time limit expired";
break;
}
// Put main code here
// Update current weight in sack every iteration of while loop
int itemsSelected = 0;
int currentWeight = 0;
for (int i = 0; i < sack.getNumObjects(); i++)
{
itemsSelected++;
currentWeight = sack.getCost(i) + currentWeight;
}
// Create random index to put into sack
srand(time(NULL));
int randNum = rand() % sack.getNumObjects();
// if item isn't selected, and there is enough space, then select item
if ((sack.isSelected(randNum) == false) && sack.getCost(randNum) + currentWeight <= sack.getCostLimit())
{
sack.select(randNum);
}
// Need an exit case where there is no more items that can fit in the sack
else if (sack.getCost(randNum) + currentWeight > sack.getCostLimit())
{
// need to record sack weight and value and items when this happens (and there are
// no more items that can legally be added)
}
}
}
/**
* Check if a knapsack contains a valid selection
* @param k the knapsack instance to check
*/
bool checkValid(knapsack &k)
{
return (k.getCost() < k.getCostLimit());
}
