题解 | 显生之宙

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

int main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    ll T;
    cin>>T;
    while(T--){
        ll n;
        cin>>n;
        vector<ll>a(n);
        for(ll i=0;i<n;i++){
            cin>>a[i];
        }
        sort(a.begin(),a.end());
        ll pre_f=0;
        for(ll i=1;i<n;i++){
            if(a[i-1]<0){
                pre_f+=a[i-1];
                a[i]+=pre_f;
            }
            else{
                a[i]+=a[i-1]+pre_f;
            }
        }
        cout<<a.back()<<'\n';
    }

    return 0;
}