(UVA) Shopaholic - Solution

Link to the problem: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2354

The solution bellow used a Greedy approach to solve this problem.

We sort the array of items in a decreasing order and, every 3 items, we sum the value of the last item (the one that would be given for free).


import java.io.*;
import java.util.*;

class Main {
    public void process() throws NumberFormatException, IOException {
        Scanner sc = new Scanner(System.in);
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int numTests = sc.nextInt();
        for (int test = 0; test < numTests; test++) {
            int numItems = sc.nextInt();
            Integer[] items = new Integer[numItems];
            for (int i = 0; i < numItems; i++) {
                items[i] = sc.nextInt();
            }
            Arrays.sort(items, Collections.reverseOrder());
           
            int totalDiscount = 0;
            for (int i = 2; i < numItems; i += 3) {
                totalDiscount += items[i];
            }
            bw.write(totalDiscount+"\n");
        }
                                              
        bw.flush();
        bw.close();
       
        return;
    }
   
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();
       
        System.exit(0);
    }
}