Witch game

#include <iostream>
#include <cstring>
#include <algorithm>
#include <set>
#include <vector>
#define long long long

using namespace std;

int N;
int acc[100001];
set<int> adj[100001];

int main() {
    ios_base::sync_with_stdio(false);

    cin >> N;
    for (int i = 0; i < N; i++) {
        int j;
        cin >> j;
        j--;
        adj[i].insert(j);
        adj[j].insert(i);
        acc[i] = j;
    }
    long total = N * (N-1) * (N-2) / 6;
    for (int i = 0; i < N; i++) {
        int j = acc[i];
        // cout << i+1 << " " << j+1 << ": " << N - adj[i] - adj[i] - 2 << "\n";
        vector<int> un;
        set_union(adj[i].begin(), adj[i].end(), adj[j].begin(), adj[j].end(), back_inserter(un));
        vector<int> in;
        set_intersection(adj[i].begin(), adj[i].end(), adj[j].begin(), adj[j].end(), back_inserter(in));
        total -= N - un.size();
        // cout << i << " " << j << ": " << un.size() << "\n";
        if (adj[i].size() > 1) total -= (adj[i].size() * (adj[i].size() - 1) / 2);
        if (in.size() > 0 && (i < in[0] && i < j)) total -= in.size();
    }
    cout << total << "\n";
    return 0;
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: WRONG ANSWER

Test 5

Group: 1

Verdict: WRONG ANSWER

Test 6

Group: 2

Verdict: WRONG ANSWER

Test 7

Group: 2

Verdict: WRONG ANSWER

Test 8

Group: 2

Verdict: WRONG ANSWER

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 3

Verdict: WRONG ANSWER

Test 12

Group: 3

Verdict: WRONG ANSWER

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER