Sorting

input/code.cpp: In function 'void usaco()':
input/code.cpp:15:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("problem.in", "r", stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp:16:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("problem.out", "w", stdout);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;
void fast() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
}
void ran() {
	srand(chrono::steady_clock::now().time_since_epoch().count());
}
long long get_rand() {
	long long a = rand();
	long long b = rand();
	return a * (RAND_MAX + 1ll) + b;
}
void usaco() {
	freopen("problem.in", "r", stdin); 
	freopen("problem.out", "w", stdout);
}
template<typename T>
using min_pq = priority_queue<T, vector<T>, greater<T>>;
// #define endl '\n'
// #define double long double
// #define int long long
// const int MOD = 1000 * 1000 * 1000 + 7;
// const int MOD = 998244353;
 
 
void solve() {
	
	int n;
	cin >> n;
	vector<int> tr(n);
	
	bool isc = true;
	
	for (int i=0; i<n; i++) {
		cin >> tr[i];
		if (tr[i] != i+1) isc = false;
	}
	
	if (isc) {
		cout << "YES" << endl;
		return;
	}
	if (n <= 3) {
		cout << "NO" << endl;
		return;
	}
	if (n == 4) {
		if (tr[0] == 3 && tr[1] == 4 && tr[2] == 1 && tr[3] == 2) cout << "YES" << endl;
		else cout << "NO" << endl;
		return;
	}
	
	int a = 0;
	for (int i=0; i<n; i++) {
		for (int j=i+1; j<n; j++) {
			if (tr[i] > tr[j]) a++;
		}
	}
	
	cout << (a % 2 == 0 ? "YES" : "NO") << endl;
	
}
 
signed main() {
	int t;
	cin >> t;
	while (t--) solve();
 
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED