Educational Codeforces Round 90 (Rated for Div. 2) F - Network Coverage 二分

#include<map>
#include<queue>
#include<time.h>
#include<limits.h>
#include<cmath>
#include<ostream>
#include<iterator>
#include<set>
#include<stack>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define rep_1(i,m,n) for(int i=m;i<=n;i++)
#define mem(st) memset(st,0,sizeof st)
int read()
{
    int res=0,ch,flag=0;
    if((ch=getchar())=='-')             //判断正负
        flag=1;
    else if(ch>='0'&&ch<='9')           //得到完整的数
        res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')
        res=res*10+ch-'0';
    return flag?-res:res;
}
typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;
typedef pair<double,double> pdd;
const int inf = 0x3f3f3f3f;
const int N=1000000 + 10;
int a[N];
int b[N];
int a1[N];
int b1[N];
int n;
int sum;
bool check(int mid)
{
    for(int i=1; i<=n; i++)
        a1[i]=a[i],b1[i]=b[i];
    a1[1]=mid;
    for(int i=1; i<=n; i++)
    {
        b1[i]-=a1[i];
        if(b1[i]<0)
            return false;
        a1[i+1]-=b1[i];
        a1[i+1]=max(a1[i+1],0);
        if(i==n)
            sum=mid+b1[i];
    }
    return true;
}
void solve()
{
    n=read();
    for(int i=1; i<=n; i++)
        a[i]=read();
    for(int i=1; i<=n; i++)
        b[i]=read();
    int l=0,r=b[1]+1;
    while(l<r)
    {
        int mid=(l+r+1)>>1;
        if(check(mid))
            l=mid;
        else
            r=mid-1;
    }
    if(!check(l))
    {
        cout<<"NO"<<endl;
        return ;
    }
    if(sum<a[1])
    {
        cout<<"NO"<<endl;
        return ;
    }
    cout<<"YES"<<endl;
}
int main()
{
    int t;
    cin>>t;
    while(t--)
        solve();
    return 0;
}