knapsack

package il.ac.tau.cs.sw1.ex7;
import java.util.*;

public class FractionalKnapSack implements Greedy<FractionalKnapSack.Item>{
    int capacity;
    List<Item> lst;

    FractionalKnapSack(int c, List<Item> lst1){
        capacity = c;
        lst = lst1;
    }

    public static class Item {
        double weight, value;
        Item(double w, double v) {
            weight = w;
            value = v;
        }

        @Override
        public String toString() {
            return "{" + "weight=" + weight + ", value=" + value + '}';
        }
    }

    public class ItemComparator implements Comparator<Item> {
        @Override
        public int compare(Item item1, Item item2) {
            double item1RelativeValue = item1.value / item1.weight;
            double item2RelativeValue = item2.value / item2.weight;
            return Double.compare(item2RelativeValue, item1RelativeValue);
        }
    }

    public double weightSum(List<Item> candidates_lst) {
        double weightSum = 0;
        for (Item item: candidates_lst) {
            weightSum += item.weight;
        }
        return weightSum;
    }

    @Override
    public Iterator<Item> selection() {
        ArrayList<Item> items = new ArrayList<Item>(); // empty list of items
        for (Item item: this.lst) { // add items
            items.add(item);
        }
        ItemComparator comp = new ItemComparator();
        Collections.sort(items, comp); // descending order
        return items.iterator(); // return iterator
    }

    @Override
    public boolean feasibility(List<Item> candidates_lst, Item element) {
        return this.capacity > weightSum(candidates_lst);
    }

    @Override
    public void assign(List<Item> candidates_lst, Item element) {
        if (weightSum(candidates_lst) + element.weight <= this.capacity) {
            candidates_lst.add(element);
        }
        else {
            double partial_weight = this.capacity - weightSum(candidates_lst);
            Item partialItem = new Item(partial_weight, element.value);
            candidates_lst.add(partialItem);
        }
    }

    @Override
    public boolean solution(List<Item> candidates_lst) {
        return this.capacity == weightSum(candidates_lst);
    }

    public static void main(String[] args) {
        Item item1 = new Item(30, 120);
        Item item2 = new Item(20, 100);
        Item item3 = new Item(10, 60);
        List<Item> items = new ArrayList<Item>();
        items.add(item1);
        items.add(item2);
        items.add(item3);
        FractionalKnapSack sack = new FractionalKnapSack(50, items);
        System.out.println(sack.greedyAlgorithm().toString());

    }
}