Maximum Alt Sum

import java.io.*; // for handling input/output
import java.util.*; // contains Collections framework

// don't change the name of this class
// you can add inner classes if needed
class Main {
    public static void main (String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt(); 
        for(int i = 0; i < t; i++) {
            int n = sc.nextInt(); 
            ArrayList<Integer> l = new ArrayList<>();
            for(int j = 0; j < n; j++) {
                int a = sc.nextInt();
                l.add(a);
            }
            ArrayList<Integer> max = new ArrayList<>();
            ArrayList<Integer> min = new ArrayList<>();
            
            while (l.size() > 1) {
                int m = Collections.max(l);
                int mi = Collections.min(l);
                max.add(m);
                min.add(mi);
                l.remove(Integer.valueOf(m));
                l.remove(Integer.valueOf(mi));
            }

           
            if (!l.isEmpty()) {
                max.add(l.get(0));
            }

            int xsum = 0;
            int nsum = 0;

            
            for (int x : max) {
                xsum += x;
            }

            
            for (int x : min) {
                nsum += x;
            }

            System.out.println(xsum - nsum);
        }
    }
}