Turtle vs. Rabbit Race: Optimal Trainings

https://codeforces.com/problemset/problem/1933/E
前缀和 + 二分查找，之前一直用三分，好像不太行？
总之找到u和u+1的就行
代码：

#include<iostream>
#include<vector>
#include<algorithm>
#include<math.h>
#include<sstream>
#include<string>
#include<string.h>
#include<iomanip>
#include<stdlib.h>
#include<map>
#include<queue>
#include<limits.h>
#include<climits>
#include<fstream>
#include<stack>
typedef unsigned long long ll;
using namespace std;
int T,n,a[100100],sum[100100];
signed main(){
    cin>>T;
    while(T--){
        cin>>n;
        for(int i=1;i<=n;i++){cin>>a[i];sum[i]=sum[i-1]+a[i];}
        int q;cin>>q;
        while(q--){
            int l,u;
            cin>>l>>u;
            int L=l,R=n;
            while(L<R){
                int mid=(L+R+1)>>1;
                if(sum[mid]-sum[l-1]<=u) L=mid;
                else R=mid-1;
            }
            L=R;
            int s1=abs(sum[L]-sum[l-1]-u),s2=abs(sum[L+1]-sum[l-1]-u);
            if(L==n) cout<<L<<" ";
            else{
                if(s1<=s2-1) cout<<L<<" ";
                else cout<<L+1<<" ";
            }
        }
        cout<<endl;
    }
    return 0;
}