Sorting

input/code.cpp: In function 'int main()':
input/code.cpp:87:20: warning: statement has no effect [-Wunused-value]
         debug(test);
                    ^

//#pragma GCC optimize("Ofast")

#include <bits/stdc++.h>

using namespace std;

void debug_out() { cerr << endl; }

template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << "[" << H << "]";
    debug_out(T...);
}

#ifdef dddxxz
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#define SZ(s) ((int)s.size())

clock_t startTime;

double getCurrentTime() {
    return (double) (clock() - startTime) / CLOCKS_PER_SEC;
}

typedef long long ll;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const double eps = 0.00001;
const int MOD = 1e9 + 7;
const int INF = 1000000101;
const long long LLINF = 1223372000000000555;
const int N = 1e6 + 3e1;
const int M = 122;

set<vector<int>> vis[10];

void dfs(vector<int> v, int n){
    vis[n].insert(v);
    for (int i = 0; i < n - 1; i++){
        for (int j = i + 2; j < n - 1; j++){
            vector<int> u = v;
            swap(u[i], u[j]);
            swap(u[i + 1], u[j + 1]);
            if (vis[n].find(u) == vis[n].end()){
                dfs(u, n);
            }
        }
    }

}

void solve(int TC) {
    int n;
    cin >> n;

    vector<int> a(n);
    for (int &i : a) cin >> i;

    if (vis[n].empty()){
        vector<int> v;
        for (int i = 1; i <= n; i++) v.push_back(i);
        dfs(v, n);
    }

    cout << (vis[n].find(a) != vis[n].end() ? "YES\n" : "NO\n");

}

int main() {
    startTime = clock();
    ios_base::sync_with_stdio(false);

    bool llololcal = false;
#ifdef dddxxz
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    llololcal = true;
#endif

    int TC = 1;
    cin >> TC;

    for (int test = 1; test <= TC; test++) {
        debug(test);
        solve(test);
    }

    if (llololcal) cerr << endl << "Time: " << getCurrentTime() * 1000 << " ms" << endl;

    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: RUNTIME ERROR

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED