Sorting

input/code.cpp: In function 'int main()':
input/code.cpp:29:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &t);
  ~~~~~^~~~~~~~~~
input/code.cpp:31:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &n);
   ~~~~~^~~~~~~~~~
input/code.cpp:32:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   for (int i = 1; i <= n; i++) scanf("%d", p + i);
                                ~~~~~^~~~~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;

int t, n, p[105];
set<vector<int>> s;

bool go(int a) {
	if (!s.insert(vector<int>(p + 1, p + a + 1)).second) return 0;
	bool ok = 1;
	for (int i = 1; i <= a; i++)
		if (p[i] != i) {
			ok = 0;
			break;
		}
	if (ok) return 1;
	for (int i = 1; i < a; i++)
		for (int j = i + 2; j < a; j++) {
			swap(p[i], p[j]);
			swap(p[i + 1], p[j + 1]);
			if (go(a)) return 1;
			swap(p[i], p[j]);
			swap(p[i + 1], p[j + 1]);
		}
	return 0;
}

int main() {
	scanf("%d", &t);
	while (t--) {
		scanf("%d", &n);
		for (int i = 1; i <= n; i++) scanf("%d", p + i);
		for (int j = n ; j >= 6; j--) {
			if (p[j] == j) continue;
			if (p[1] == j) {
				swap(p[1], p[j - 1]);
				swap(p[2], p[j]);
			}
			if (p[j - 1] == j) {
				swap(p[j - 1], p[j - 3]);
				swap(p[j], p[j - 2]);
				swap(p[j - 3], p[j]);
				swap(p[j - 4], p[j - 1]);
				continue;
			}
			for (int k = 2; k <= j - 2; k++)
				if (p[k] == j) {
					swap(p[k - 1], p[j - 1]);
					swap(p[k], p[j]);
					break;
				}
		}
		s.clear();
		puts(go(min(n, 6)) ? "YES" : "NO");
	}
}

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