Järjestäminen

#include <iostream>
 
using namespace std;
 
int64_t t, n, l[100], s;
 
int main() {
	cin >> t;
	for (int64_t i = 0; i < t; i++) {
		cin >> n;
		for (int64_t j = 0; j < n; j++) {
			cin >> l[j];
		}
		if (n == 2) {
			cout << (l[0] < l[1]? "YES" : "NO") << endl;
			continue;
		}
		if (n == 3) {
			cout << (l[0] < l[1] && l[1] < l[2]? "YES" : "NO") << endl;
			continue;
		}
		if (n == 4) {
			cout << ((l[0] < l[1] && l[1] < l[2] && l[2] < l[3]) || (l[2] < l[3] && l[3] < l[0] && l[0] < l[1])? "YES" : "NO") << endl;
			continue;
		}
		s = 0;
		for (int64_t j = 0; j < n; j++) {
			for (int64_t k = j + 1; k < n; k++) {
				if (l[k] < l[j]) {
					s++;
				}
			}
		}
		cout << (s % 2 == 0? "YES" : "NO") << endl;
	}
}

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