1443D - Extreme Subtraction - CodeForces Solution

#include <iostream>
using namespace std;
const int N = 1e6 + 10;
int a[N];
int n, sum;
int main()
{
	int T;
	cin >> T;
	while(T--)
	{
		cin >> n;
		for(int i = 1;i <= n;i++) cin >> a[i];
		for(int i = n;i >= 1;i--) a[i] -= a[i - 1];
		sum = 0;
		for(int i = 2;i <= n;i++) if(a[i] < 0) sum -= a[i];
		if(a[1] >= sum) cout << "YES";
		else cout << "NO";
		if(T != 0) cout << endl;
	}
	return 0;
}