PAT甲级1128

#include<iostream>
#include<cmath>
#include<vector>
using namespace std;

int fun(vector<int> arr)
{
	int len = arr.size();
	for (int i = 1; i < len; i++)
	{
		for (int j = 0; j < i; j++)
		{
			if (abs(arr[i] - arr[j]) == abs(i - j) || arr[i] == arr[j]) return 0;
		}
	}
	return 1;
}

int main()
{
	int n, m, a;
	vector<int> q;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> m;
		q.clear();
		for (int j = 0; j < m; j++)
		{
			cin >> a;
			q.push_back(a);
		}
		if (fun(q) == 0) cout << "NO\n";
		else if (fun(q) == 1) cout << "YES\n";
	}	
}