1694C - Directional Increase - CodeForces Solution

//In the name of God
#include <bits/stdc++.h>
using namespace std;

const int maxn = 2e5 + 100;

#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

int n, t, a[maxn];
long long ps[maxn];

int main(){
	fast_io;
	
	cin >> t;
	while(t--){
		cin >> n;
		for(int i = 1; i <= n; i++){
			cin >> a[i];
			ps[i] = ps[i - 1] + a[i];
		}
		if(ps[n] != 0){
			cout << "No\n";
			continue;
		}
		bool ok = 1;
		for(int i = 1; i <= n; i++){
			if(ps[i] < 0) ok = 0;
		}
		bool visited_zero = 0;
		for(int i = 1; i <= n; i++){
			if(ps[i] == 0) visited_zero = 1;
			else if(visited_zero) ok = 0;
		}
		if(ok) cout << "Yes\n";
		else cout << "No\n";
	}
	
	return 0;
}