Freshman's Database

#include <iostream>
#include <algorithm>
#include <cstdio>

using namespace std;

int cur_color = 1;
int counter = 0;
int is[1000005];
vector<int> v;

void go(int i) {
    is[i] = cur_color;
    int next = v[i];
    while (true) {
        if (is[next] == 0) {
            is[next] = cur_color;
            next = v[next];
        } else if (is[next] == cur_color) {
            counter += 1;
            break;
        } else {
            break;
        }
    }
}

int main(int argc, char *argv[])
{
    int n = 0;
    cin >> n;

    for (int i = 0; i < n; ++i) {
        int x = 0;
        cin >> x;
        v.push_back(x - 1);
    }

    for (int i = 0; i < n; ++i) {
        if (is[i] == 0) {
//            cout << i << " " << counter << endl;
            go(i);
            cur_color += 1;
        }
    }

    cout << counter << 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