Noitapeli

#include <bits/stdc++.h>

#define ll long long

using namespace std;

bool b[5555][5555];
vector<pair<int, int>> v;
int a[5555];

int main () {
	ll ans = 0;
	int n;
	cin>>n;
	for (int i = 1; i <= n; i++) {
		int x;
		cin>>x;
		if (!b[i][x]) {
			b[i][x] = b[x][i] = 1;
			a[i]++;
			a[x]++;
			v.push_back({i, x});
		}
		b[i][i] = 1;
	}
	for (int i = 1; i <= n; i++) {
		ans += (n - a[i] - 1) * (n - a[i] - 2) / 2;
		//cout<<i<<" "<<ans<<endl;
		for (auto p : v) {
			if (!b[i][p.first] && !b[i][p.second]) ans--;
		}
		for (int j = 1; j <= n; j++) {
			if (!b[i][j]) {
				b[i][j] = b[j][i] = 1;
				a[j]++;
				a[i]++;
			}
		}
		//cout<<i<<" "<<ans<<endl;
	}
	cout<<ans<<endl;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: RUNTIME ERROR

Test 12

Group: 3

Verdict: RUNTIME ERROR

Test 13

Group: 3

Verdict: RUNTIME ERROR

Test 14

Group: 3

Verdict: RUNTIME ERROR

Test 15

Group: 3

Verdict: RUNTIME ERROR