Witch game

#include <functional>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
using namespace std;
#define rep(i,a,b) for(int i = (a); i < int(b); ++i)
#define rrep(i,a,b) for(int i = (b); i --> int(a); )
#define trav(i,v) for(auto&i:v)
#define all(c) (c).begin(), (c).end()
#define sz(c) int((c).size())
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
int main(){
	cin.tie(0);
	cin.sync_with_stdio(0);
	ll n;
	cin >> n;
	set<pii> E;
	vi v(n),c(n);
	rep(i,0,n){
		int j;
		cin >> j;
		--j;
		v[i] = j;
		pii e = {min(i,j),max(i,j)};
		if(E.find(e) == E.end()) E.insert(e);
	}
	ll ans = 0;
	rep(i,0,n)
		ans += i == v[v[v[i]]];
	ans /= 3;
	trav(i,E)
		ans += n-2-c[i.first]++-c[i.second]++;

	cout << n*(n-1)*(n-2)/6-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: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED