#include <bits/stdc++.h> #include <atcoder/all> using namespace std; using namespace atcoder; typedef int64_t lint; #define rep(i, n) for(int i=0; i<n; i++) #define repx(i, l, n) for(int i=l; i<n; i++) #define all(v) v.begin(), v.end() #define show(x) cout << #x << ": " << x << endl; #define list(x) cout << #x << ": " << x << " "; #define pb push_back using vi = vector<lint>; using vvi = vector<vector<lint>>; template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); } template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } template<class T> inline void drop(T x) { cout << x << endl; exit(0); } template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; } constexpr lint LINF = LLONG_MAX/2; int main() { lint T; cin >> T; rep(_, T) { lint N; cin >> N; vi v(N); vin(v); lint a=0, b=0, c=0, x, y, z; sort(all(v), greater()); if (N%2 == 0) { rep(i, N/2) { a += v[i*2]; a -= v[i*2+1]; } std::cout << a << '\n'; } else { rep(i, N/2) { chmax(b, a+v[i+N/2]); a += v[i*2]; a -= v[i*2+1]; } chmax(b, a+v[N-1]); std::cout << b << '\n'; } } }