Sorting

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 105;
using lint = long long;

void solve(){
	int n; cin >> n;
	vector<int> a(n);
	for(auto &i : a) cin >> i;
	int ret = 0;
	for(int i=0; i<n; i++){
		for(int j=i+1; j<n; j++){
			if(a[j] < a[i]) ret++;
		}
	}
	if(n <= 3){
		puts(ret ? "NO" : "YES");
	}
	else if(n > 4){
		puts(ret % 2 ? "NO" : "YES");
	}
	else{
		if(is_sorted(a.begin(), a.end())) puts("YES");
		else{
			swap(a[0], a[2]);
			swap(a[1], a[3]);
			puts(is_sorted(a.begin(), a.end()) ? "YES" : "NO");
		}
	}
}

int main(){
	int t; cin >> t;
	while(t--) solve();
}

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