Code test - Maximize cost for a given weight of a Package

Question

You want to send your friend a package with different things. Each thing you put inside the package has such parameters as index number, weight and cost. The package has a weight limit. Your goal is to determine which things to put into the package so that the total weight is less than or equal to the package limit and the total cost is as large as possible.

You would prefer to send a package which weights less in case there is more than one package with the same price.

INPUT SAMPLE:

Your program should accept as its first argument a path to a filename. The input file contains several lines. Each line is one test case.

Each line contains the weight that the package can take (before the colon) and the list of things you need to choose. Each thing is enclosed in parentheses where the 1st number is a thing's index number, the 2nd is its weight and the 3rd is its cost. Eg:

81 : (1,53.38,45)(2,88.62,98) (3,78.48,3)(4,72.30,76) (5,30.18,9)(6,46.34,48) 
8 : (1,15.3,34)
75:(1,85.31,29) (2,14.55,74)(3,3.98,16) (4,26.24,55)(5,63.69,52) (6,76.25,75)(7,60.02,74) (8,93.18,35)(9,89.95,78) 
56 : (1,90.72,13)(2,33.80,40) (3,43.15,10)(4,37.97,16) (5,46.81,36)(6,48.77,79) (7,81.80,45)(8,19.36,79) (9,6.76,$64)

OUTPUT SAMPLE:

For each set of things that you put into the package provide a list (items’ index numbers are separated by comma). E.g.

4 //for package1
- //for package2
2,7 //for package3
8,9 //for package4

CONSTRAINTS:

Max weight that a package can take is ≤ 100 There might be up to 15 items you need to choose from Max weight and cost of an item is ≤ 100

Is there a more elegant and easy to understand solution than https://discuss.codechef.com/questions/104934/package-problemin-java

Can be solved by using [Powerset question](https://stackoverflow.com/questions/4640034/calculating-all-of-the-subsets-of-a-set-of-numbers) concept — firstpostcommenter, Apr 14 '18 at 08:51
Now we can loop through all combinations and see which item combination has the maximum consolidated cost and minimum consolidated weight and is within the Package weight limit — firstpostcommenter, Apr 15 '18 at 07:18
First remove the items whose weight is greater than the package weight limit since those items are not eligible to be placed inside the package. Do this before applying the powerset combinations generation logic — firstpostcommenter, Apr 15 '18 at 07:20

score 1 · Answer 1 · answered Aug 18 '19 at 21:47

Here is the code (KnapSack):

public class FriendPackageKnapsack {

    public static void parserThings(String[] sub2, List<Package> things, 
            double maxWeight) {
        for (int i = 0; i < sub2.length; i++) {
            String[] sub3 = (sub2[i].substring(1, sub2[i].length() - 1)).split(",");
            int id = Integer.parseInt(sub3[0]);
            double weight = Double.parseDouble(sub3[1]);
            double cost = Double.parseDouble(sub3[2].substring(1, sub3[2].length()));
            if (weight <= maxWeight) {
                Package condidat = new Package(id, weight, cost);
                things.add(condidat);
            }
        }
    }

    public static String getOptimumFor(List<Package> things, int r, int maxWt) {
        int indexSolution = 0;
        String returnData = "";
        double maxWeight = 0;
        double maxCost = 0;
        int[] data = new int[r];
        List<Integer> res = new ArrayList<Integer>();
        int[] arr = new int[things.size()];
        for (int i = 0; i < things.size(); i++) {
            arr[i] = i;
        }
        getCombination(arr, data, res, 0, 0);

        for (int i = 0; i <= res.size() - r; i += r) {
            double someWeight = 0;
            double someCost = 0;
            for (int j = 0; j < r; j++) {
                someWeight += things.get(res.get(i + j)).getWeight();
                someCost += things.get(res.get(i + j)).getCost();
            }
            if (someWeight <= maxWt) {
                if ((someCost > maxCost)
                        || ((someCost == maxCost) && (someWeight <= maxWeight))) {
                    indexSolution = i;
                    maxWeight = someWeight;
                    maxCost = someCost;
                }
            }
        }
        for (int k = indexSolution; k < r + indexSolution; k++) {
            returnData += res.get(k) + ",";
        }
        return returnData + maxCost + "," + maxWeight;
    }

    public static void getCombination(int[] arr, int[] data, List<Integer> res, int start,
            int index) {
        if (index == data.length) {
            for (int j = 0; j < data.length; j++) { res.add(data[j]); }
            return;
        }
        for (int i = start; i < arr.length && arr.length - i >= data.length - index; i++) {
            data[index] = arr[i];
            getCombination(arr, data, res, i + 1, index + 1);
        }
    }

    public static void main(String[] args) {
        File file = new File("packageproblem.txt");
        BufferedReader in = null;
        try {
            in = new BufferedReader(new FileReader(file));
        } 
        catch (FileNotFoundException e) { e.printStackTrace(); }
        String line = "";
        List<Package> things = new ArrayList<>();
        try {
            while ((line = in.readLine()) != null) {
                String s = "";
                // Parsing line
                String[] sub1 = line.split(" : ");
                int N = Integer.parseInt(sub1[0]);
                String[] sub2 = sub1[1].split(" ");
                if (sub2.length > 1) {
                    things.clear();
                    parserThings(sub2, things, N);

                    double maxCost = 0;
                    double maxWeight = 0;
                    for (int i = 1; i <= things.size(); i++) {
                        String resultat = getOptimumFor(things, i, N);
                        // System.out.println(resultat);
                        String[] sub4 = resultat.split(",");
                        double cost = Double.parseDouble(sub4[sub4.length - 2]);
                        double weight = Double.parseDouble(sub4[sub4.length - 1]);
                        if (cost == maxCost) {
                            if (weight < maxWeight) {
                                maxCost = cost;
                                maxWeight = weight;
                                s = resultat;
                            }
                        }
                        if (cost > maxCost) {
                            maxCost = cost;
                            maxWeight = weight;
                            s = resultat;
                        }  
                    }
                    // System.out.println(s);
                    String[] sub5 = s.split(",");
                    String ss = "";
                    for (int i = 0; i < sub5.length - 2; i++) {
                        ss += things.get(Integer.parseInt(sub5[i])).getId() + ",";
                    }
                    if (ss.equals("")) { System.out.println("-"); }
                    else { System.out.println(ss.substring(0, ss.length() - 1)); }

                } 
                else {  System.out.println("-"); }
            }

        } 
        catch (IOException e) { e.printStackTrace(); }
    }
}

class Package {
    private int id;
    private double weight;
    private double cost;

    public Package(int id, double weight, double cost) {
        this.id = id;
        this.weight = weight;
        this.cost = cost;
    }

    public int getId() { return id; }

    public void setId(int id) { this.id = id; }

    public double getWeight() { return weight; }

    public void setWeight(double weight) { this.weight = weight; }

    public double getCost() { return cost; }

    public void setCost(double cost) { this.cost = cost; }
}

The code is taken from here.

score 1 · Answer 2 · answered Aug 12 '21 at 18:42

1

You can find a full solution of this problem in java here https://github.com/rantibi/package-challenge

answered Aug 12 '21 at 18:42

amit ghosh

81
7

Code test - Maximize cost for a given weight of a Package

2 Answers2