#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int T,N,A[202020];
void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>T;
	while(T--) {
		cin>>N;
		FOR(i,N) cin>>A[i];
		
		sort(A,A+N);
		
		int iseven=0;
		if(N%2==0) {
			iseven=A[N-1];
			N--;
			
		}
		
		int sum=A[0];
		multiset<int> S;
		for(i=1;i<N;i+=2) {
			x=A[i]-A[i-1];
			y=A[i+1]-A[i];
			S.insert(x);
			S.insert(y);
			sum+=*S.rbegin();
			S.erase(S.find(*S.rbegin()));
		}
		
		if(iseven) sum=iseven-sum;
		cout<<sum<<endl;
	}
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}