Sorting

#include <bits/stdc++.h>
using namespace std;
 
set<int> vis;
int geh(const vector<int>& v) {
  int num = 0;
  const int n = (int)v.size();
  for (int i = 0; i < n; ++i) {
    num *= 10;
    num += v[i];
  }
  return num;
}
 
int sz;
void go(vector<int>& arr) {
  int h = geh(arr);
  if (vis.find(h) != vis.end()) return;
  vis.insert(h);
  for (int i = 0; i < sz; ++i) {
    for (int j = 2+i; 1+j < sz; ++j) {
      swap(arr[i], arr[j]);
      swap(arr[1+i], arr[1+j]);
      go(arr);
      swap(arr[i], arr[j]);
      swap(arr[1+i], arr[1+j]);
    }
  }
}
 
int main() {
  ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  vector<int> arr;
  for (int i = 1; i <= 5; ++i) {
    arr.push_back(i);
    sz = (int)arr.size();
    go(arr);
  }
  /*sort(arr.begin(), arr.end());
  do {
    int h = geh(arr);
    bool in = vis.find(h) != vis.end();
    for (auto x : arr) cout << x << ' ';
    cout << in << '\n';
  } while (next_permutation(arr.begin(), arr.end()));
  vector<int> hmany(10,0);
  for (auto x : vis) {
    int len = 0;
    cout << x << endl;
    while (x%10) {
      x /= 10;
      len++;
    }
    hmany[len]++;
  }
  for (int i = 1; i <= 9; ++i) cout << i << " " << hmany[i] << endl;
  return 0;*/
  int tc; cin >> tc;
  while (tc--) {
    int n; cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) cin >> a[i];
    int h = geh(a);
    bool ok = false;
    if (n <= 5) {
      ok = vis.find(h) != vis.end();
    } else {
      int ni = 0;
      for (int i = 0; 1+i < n; ++i) {
        ni += a[i] > a[1+i];
      }
      ok = (ni%2 == 0);
    }
    cout << (ok ? "YES" : "NO") << '\n'; 
  }
  return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: WRONG ANSWER

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 1, 2

Verdict: WRONG ANSWER