Sorting

#include <bits/stdc++.h>
#include <climits>
 
using namespace std;
 
template<class T>
using V = vector<T>;
template<class T>
using VV = V<V<T>>;
 
using ld = long double;
#define ll long long
using ull = unsigned ll;
using PLL = pair<ll, ll>;
using VLL = V<ll>;
using VB = V<bool>;
using VVB = VV<bool>;
using VVLL = VV<ll>;
using Gr = VVLL;
using MLL = map<ll, ll>;
#define UMLL unordered_map<ll, ll, custom_hash>
 
//using int128 = __int128;
//using double128 = __float128;
 
#define fast ios_base::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr); cerr.tie(nullptr);
 
#define INF LONG_MAX
#define MINF LONG_MIN
 
#define R &
#define CR const R
 
#define FORI(i, a, b) for(ll i = a, max##i = b; i < max##i; ++i)
#define FOR(i, n) FORI(i, 0, n)
#define RFORI(i, a, b) for(ll i = a, min##i = b; i >= min##i; --i)
#define RFOR(i, n) RFORI(i, n, 0)
#define FORA(i, a) for(auto i : a)
#define FORAR(i, a) for(auto R i : a)
#define FORACR(i, a) for(auto CR i : a)
#define ALL(obj) begin(obj), end(obj)
#define Count(q) while(q--)
#define OK cerr << "OK\n";
 
#define mp make_pair
#define pb push_back
 
//#define DEBUG
 
template<class T>
T sqr(T x)
{
    return x * x;
}
 
void YES(bool g, ostream R os, bool upper = true)
{
    if(g)
        if(upper)
            os << "YES";
        else
            os << "Yes";
    else
        if(upper)
            os << "NO";
        else
            os << "No";
 
    os << "\n";
}
 
template<class T>
void show(T CR t, ostream R os = cerr)
{
    FORACR(i, t)
        os << i << " ";
    os << "\n";
}
 
template<class T>
void show2d(T CR t, ostream R os = cerr)
{
    FORACR(i, t)
        show(i, os);
    os << "\n";
}
 
constexpr ll MOD = 1e9 + 7;
constexpr ll len = 'z' - 'a' + 1;
 
constexpr ld PI = atanl(1.0L) * 4;
 
struct custom_hash
{
    static uint64_t splitmix64(uint64_t x)
    {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }
 
    size_t operator() (uint64_t x) const
    {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
 
ll _mergeSort(VLL R arr, VLL R temp, ll left, ll right);
ll merge(VLL R arr, VLL R temp, ll left, ll mid, ll right);
 
ll getInv(VLL R a)
{
    ll n = a.size();
 
	VLL temp(n);
	return _mergeSort(a, temp, 0, n - 1);
}
 
ll _mergeSort(VLL R a, VLL R temp, ll left, ll right)
{
	ll mid, inv_count = 0;
	if (right > left)
	{
		mid = (right + left) / 2;
 
		inv_count = _mergeSort(a, temp, left, mid);
		inv_count += _mergeSort(a, temp, mid + 1, right);
 
		inv_count += merge(a, temp, left, mid + 1, right);
	}
 
	return inv_count;
}
 
ll merge(VLL R a, VLL R temp, ll left, ll mid, ll right)
{
	ll i, j, k;
	ll inv_count = 0;
 
	i = left;
	j = mid;
	k = left;
	while ((i <= mid - 1) && (j <= right))
	{
		if (a[i] <= a[j])
		{
			temp[k++] = a[i++];
		}
		else
		{
			temp[k++] = a[j++];
 
			inv_count = inv_count + (mid - i);
		}
	}
 
	while (i <= mid - 1)
		temp[k++] = a[i++];
 
	while (j <= right)
		temp[k++] = a[j++];
 
	for (i = left; i <= right; i++)
		a[i] = temp[i];
 
	return inv_count;
}
 
//arr
unordered_set<string> dp;
 
void BFS(string s)
{
    ll n = s.size();
 
    queue<string> q;
 
    auto add = [&q](string CR t)
    {
        q.push(t);
        dp.insert(t);
    };
 
    add(s);
    while(!q.empty())
    {
        s = q.front(); q.pop();
 
        FOR(i, n - 1)
            FORI(j, i + 2, n - 1)
            {
                string t = s;
                swap(t[i], t[j]);
                swap(t[i + 1], t[j + 1]);
 
                if(dp.find(t) == dp.end())
                    add(t);
            }
    }
}
 
void init()
{
    string s;
    FOR(i, 9)
    {
        //cerr << s << "\n";
        BFS(s);
 
        s += char(i + '1');
    }
}
 
void solve(istream R is, ostream R os)
{
    ll n;
    is >> n;
 
    VLL a(n);
    FORAR(i, a)
        is >> i;
 
    if(n <= 8)
    {
        string s;
        FORACR(i, a)
            s += char(i + '0');
 
        YES(dp.find(s) != dp.end(), os, 1);
        return;
    }
 
    YES(getInv(a) % 2 == 0, os, 1);
}
 
void tester(istream R is, ostream R os)
{
    fast
    init();
    ll q = 1;
    is >> q;
    os << setprecision(999);
 
    Count(q)
        solve(is, os);
}
 
int main()
{
    //ifstream in("input.txt");
    //ofstream out("output.txt");
 
    tester(cin, cout);
}

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