WA求助

#include<bits/stdc++.h>
using namespace std;
int arr[100005];
int main(){
	int a,b,c=0,d=0;
	cin>>a;
	for(int i=1;i<=a;i++){
		cin>>b;
		for(int i=1;i<=b;i++){
			cin>>arr[i];
		}
		if(arr[i+1]*2==arr[i+2]){
			cout<<"yes"<<"\n";
		}
		else{
			cout<<"no"<<"\n";
		}		
	}
	return 0;
}