#include <bits/stdc++.h>
using namespace std;

const int MAX = int(2e5);
const int RND = 853846273;

long long A[MAX + 5], dp[MAX + 5];

long long solve(int turn, int n)
{
    if (turn == n)
        return 0;
    
    int pos = turn;
    
    if (dp[pos] != RND)
        return dp[pos];
    
    long long res = 0;
    
    if (turn % 2 == 0)
        res = max(0LL, A[pos] + solve(turn + 1, n));
    else
        res = min(0LL, solve(turn + 1, n) - A[pos]);
    
    return dp[pos] = res;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL);

    int t;
    cin >> t;

    while (t--)
    {
        int n;
        cin >> n;
        
        for (int i = 0; i < n; i++)
        {
            cin >> A[i];
            dp[i] = RND;
        }
        
        sort (A, A + n, greater<>());
        
        long long res = A[0] - A[1] + solve(2, n);
        
        cout << res << "\n";
    }

    return 0;
}