Sorting

#include <bits/stdc++.h>
#define X first
#define Y second
#define sz(a) (int)a.size()
#define pb push_back
 
using namespace std;
typedef long long ll;
 
void solve();
 
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}
 
int a[110];
int b[110];
 
set <vector <int>> s;
 
void solve() {
    s.clear();
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
        b[i] = a[i];
    }
    sort(b, b + n);
    for (int i = 0; i < n; ++i) {
        if (n - i <= 5) {
            deque <vector <int>> d;
            d.pb({});
            for (int j = i; j < n; ++j) {
                d.back().pb(a[j]);
            }
            s.insert(d.back());
            vector <int> f = d.back();
            sort(f.begin(), f.end());
            while (sz(d) > 0) {
                vector <int> t = d.front();
                if (t == f) {
                    cout << "YES\n";
                    return;
                }
                d.pop_front();
                for (int i = 0; i < sz(t) - 1; ++i) {
                    for (int j = i + 2; j < sz(t) - 1; ++j) {
                        swap(t[i], t[j]);
                        swap(t[i + 1], t[j + 1]);
                        if (s.count(t) == 0) {
                            s.insert(t);
                            d.pb(t);
                        }
                        swap(t[i], t[j]);
                        swap(t[i + 1], t[j + 1]);
                    }
                }
            }
            break;
        }
        if (a[i] == b[i])
            continue;
        bool f = false;
        for (int j = i + 2; j < n - 1; ++j) {
            if (a[j] == b[i]) {
                swap(a[j], a[i]);
                swap(a[j + 1], a[i + 1]);
                f = true;
                break;
            }
        }
        if (!f) {
            if (b[i] == a[n - 1]) {
                if (n - 4 >= i) {
                    swap(a[n - 1], a[n - 3]);
                    swap(a[n - 2], a[n - 4]);
                    for (int j = i + 2; j < n - 1; ++j) {
                        if (a[j] == b[i]) {
                            swap(a[j], a[i]);
                            swap(a[j + 1], a[i + 1]);
                            f = true;
                            break;
                        }
                    }
                    if (!f) {
                        cout << "NO" << endl;
                        return;
                    }
                } else {
                    cout << "NO" << endl;
                    return;
                }
            } else {
                if (n - 4 >= i) {
                    swap(a[i], a[i + 2]);
                    swap(a[i + 1], a[i + 3]);
                    for (int j = i + 2; j < n - 1; ++j) {
                        if (a[j] == b[i]) {
                            swap(a[j], a[i]);
                            swap(a[j + 1], a[i + 1]);
                            f = true;
                            break;
                        }
                    }
                    if (!f) {
                        cout << "NO" << endl;
                        return;
                    }
                } else {
                    cout << "NO" << endl;
                    return;
                }
            }
        }
    }
    cout << "NO" << endl;
    return;
}

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