// N <= 12 では bit dp の愚直解をやる
// 想定解壊れてないかチェック
#include <algorithm>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;

using lint = long long;

lint bitdp(int N, vector<lint> A) {
    for (int i = N - 1; i; --i) A[i] -= A[i - 1];
    vector<lint> dp(1 << N);
    const lint INF = (1LL << 60) - 1;
    for (int S = 1; S < 1 << N; ++S) {
        bool is_senteban = ((N & 1) == (__builtin_popcount(S) & 1));
        if (is_senteban) {
            dp[S] = -INF;
        } else {
            dp[S] = INF;
        }
        for (int i = 0; i < N; ++i) {
            if (((S >> i) & 1) == 0) continue;
            int addval = 0;
            if (is_senteban and S - (1 << i) < (1 << i)) {
                int cur = i;
                while (cur >= 0 and ((S - (1 << i)) & (1 << cur)) == 0) {
                    addval += A[cur];
                    --cur;
                }
            }
            if (is_senteban) {
                dp[S] = max(dp[S], dp[S - (1 << i)] + addval);
            } else {
                dp[S] = min(dp[S], dp[S - (1 << i)]);
            }
        }
    }
    return dp.back();
}

lint ac_solution(const vector<lint> &A) {
    const int N = A.size();
    priority_queue<lint> pq;
    lint last = 0;
    for (int i = 0; i < N; ++i) {
        pq.push(A[i] - (i ? A[i - 1] : 0));
        if (i % 2 == 0) {
            last += pq.top();
            pq.pop();
        }
    }
    return N % 2 ? last : A.back() - last;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int T;
    cin >> T;
    while (T--) {
        int N;
        cin >> N;
        vector<lint> A(N);
        for (auto &x : A) cin >> x;
        sort(A.begin(), A.end());
        if (N <= 12) {
            lint sol_brutefore = bitdp(N, A);
            lint ans = ac_solution(A);
            if (sol_brutefore != ans) {
                cerr << sol_brutefore << ' ' << ans << ' ' << N;
                for (auto a : A) cerr << ' ' << a;
                cerr << endl;
                throw;
            }
            cout << ans << '\n';
        } else {
            cout << ac_solution(A) << '\n';
        }
    }
}