链接：https://codeforces.com/contest/1285/problem/B
Today, Yasser and Adel are at the shop buying cupcakes. There are nn cupcake types, arranged from 11 to nn on the shelf, and there are infinitely many of each type. The tastiness of a cupcake of type ii is an integer aiai. There are both tasty and nasty cupcakes, so the tastiness can be positive, zero or negative.
Yasser, of course, wants to try them all, so he will buy exactly one cupcake of each type.
On the other hand, Adel will choose some segment [l,r][l,r] (1≤l≤r≤n)(1≤l≤r≤n) that does not include all of cupcakes (he can't choose [l,r]=[1,n][l,r]=[1,n]) and buy exactly one cupcake of each of types l,l+1,…,rl,l+1,…,r.
After that they will compare the total tastiness of the cupcakes each of them have bought. Yasser will be happy if the total tastiness of cupcakes he buys is strictly greater than the total tastiness of cupcakes Adel buys regardless of Adel's choice.
For example, let the tastinesses of the cupcakes be [7,4,−1][7,4,−1]. Yasser will buy all of them, the total tastiness will be 7+4−1=107+4−1=10. Adel can choose segments [7],[4],[−1],[7,4][7],[4],[−1],[7,4] or [4,−1][4,−1], their total tastinesses are 7,4,−1,117,4,−1,11 and 33, respectively. Adel can choose segment with tastiness 1111, and as 1010 is not strictly greater than 1111, Yasser won't be happy :(
Find out if Yasser will be happy after visiting the shop.
Input
Each test contains multiple test cases. The first line contains the number of test cases tt (1≤t≤1041≤t≤104). The description of the test cases follows.
The first line of each test case contains nn (2≤n≤1052≤n≤105).
The second line of each test case contains nn integers a1,a2,…,ana1,a2,…,an (−109≤ai≤109−109≤ai≤109), where aiai represents the tastiness of the ii-th type of cupcake.
It is guaranteed that the sum of nn over all test cases doesn't exceed 105105.
Output
For each test case, print "YES", if the total tastiness of cupcakes Yasser buys will always be strictly greater than the total tastiness of cupcakes Adel buys regardless of Adel's choice. Otherwise, print "NO".
Example
input
Copy
3 4 1 2 3 4 3 7 4 -1 3 5 -5 5
output
Copy
YES NO NO
Note
In the first example, the total tastiness of any segment Adel can choose is less than the total tastiness of all cupcakes.
In the second example, Adel will choose the segment [1,2][1,2] with total tastiness 1111, which is not less than the total tastiness of all cupcakes, which is 1010.
In the third example, Adel can choose the segment [3,3][3,3] with total tastiness of 55. Note that Yasser's cupcakes' total tastiness is also 55, so in that case, the total tastiness of Yasser's cupcakes isn't strictly greater than the total tastiness of Adel's cupcakes.
代码：
#include<bits/stdc++.h>
using namespace std;
long long n,k,t,mod=1e9+7,s,ans=0;
long long a[100001],b[100001];
int main()
{
cin>>t;
while(t--)
{
cin>>n;
s=0;
ans=0;
int flag=1,l=1,r=1;
for(int i=1;i<=n;i++)
{
cin>>a[i];
s+=a[i];
b[i]=s;
}
for(int i=1;i<n;i++)
{
ans=max(ans+a[i],a[i]);
if(ans>=s)
flag=0;
}
ans=0;
for(int i=2;i<=n;i++)
{
ans=max(ans+a[i],a[i]);
if(ans>=s)
flag=0;
}
if(flag==1)
cout<<"YES"<<endl;
else
cout<<"NO"<<endl;
}
}
