#include #include #include #include #include #include #include #include #include #include #include #include #include #define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl; #define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl; template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } using namespace std; typedef long long ll; template vector> vec2d(int n, int m, T v){ return vector>(n, vector(m, v)); } template vector>> vec3d(int n, int m, int k, T v){ return vector>>(n, vector>(m, vector(k, v))); } template void print_vector(vector v, char delimiter=' '){ if(v.empty()) { cout << endl; return; } for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter; cout << v.back() << endl; } void solve(){ int n; cin >> n; vector a(n); for(int i = 0; i < n; i++) cin >> a[i]; a.push_back(0); sort(a.begin(), a.end()); vector b; for(int i = 0; i < n; i++){ b.push_back(a[i+1]-a[i]); } multiset st; ll ans = 0; for(int i = 0; i < n; i++){ st.insert(b[i]); if(i%2 == (n-1)%2){ ll x = *prev(st.end()); ans += x; st.erase(st.find(x)); } } cout << ans << endl; } int main(){ ios::sync_with_stdio(false); cin.tie(0); cout << setprecision(10) << fixed; int t; cin >> t; while(t--) solve(); }