Sorting

#include <bits/stdc++.h>
using namespace std;
//#define int long long
int a[100], pos[100], n, ok, t;
signed main(){
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    cin >> t;
    while(t--){
        cin >> n;
        ok=1;
        for(int i=0; i<n; ++i) cin >> a[i];
        for(int i=0; i<n; ++i) --a[i];
        if(n<4){
            for(int i=0; i<n; ++i) if(a[i]!=i) ok = 0;
            if(ok) cout << "YES\n";
            else cout << "NO\n";
            continue;
        }
        if(n==4){
            if(a[0]==0 && a[1]==1 && a[2]==2 && a[3]==3){
                cout << "YES\n";
            }else if(a[0]==2 && a[1]==3 && a[2]==0 && a[3]==1){
                cout << "YES\n";
            }else{
                cout << "NO\n";
            }continue;
            
        }
        int sum=0;
        for(int i=0; i<n; ++i){
            for(int j=0; j<i; ++j){
                sum += a[j]>a[i];
            }
        }
        if(sum&1) cout << "NO\n";
        else cout << "YES\n";
    }
 
}

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