Freshman's Database

#include <bits/stdc++.h>

#define ll long long
#define vi vector<int>

using namespace std;

int p[1000001];
int s[1000001];
int cc=0;

void rec(int node) {
	if(s[node] == 2) return;
	if(s[node] == 1) {
		cc++;
		return;
	}
	s[node] = 1;
	rec(p[node]);
	s[node] = 2;
}

int main() {
	int n;
	cin >> n;
	for(int i=0;i<n;i++) {
		cin >> p[i];
		p[i]--;
	}
	for(int i=0;i<n;i++)
		rec(i);
	cout << cc << endl;
	return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED