C. Theofanis' Nightmare

原题链接

题解

太巧妙了！！
层加式？

code

#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll a[100005]={0};
int main()
{
    ll t;
    cin>>t;
    while(t--)
    {
        ll n;
        cin>>n;
        for(int i=1;i<=n;i++) cin>>a[i];
        ll suf=a[n],ans=a[n];
        for(int i=n-1;i>=1;i--)
        {
            ans+=max(a[i],a[i]+suf);
            suf+=a[i];
        }
        cout<<ans<<endl;
    }
    return 0;
}