Freshman's Database

#include <bits/stdc++.h>

using namespace std;

int parent[1000010];
int nr_kolejki[1000010];
bool na_cyklu[1000010];
bool odw[1000010];
int cykle=0;

queue<int> kol;

void DFS(int x,int nr){
odw[x]=true;
nr_kolejki[x]=nr;
kol.push(x);
int pomo;
if(odw[parent[x]]==false){
    DFS(parent[x],nr);
}else{
    if(nr_kolejki[parent[x]]==nr){
        cykle++;
        while(kol.empty()==false){
            pomo=kol.front();
            na_cyklu[pomo]=true;
            kol.pop();
        }
    }else{
    while(kol.empty()==false) kol.pop();
    }
}
return;
}

int main()
{
    int n;
    cin >> n;
    int a;
    for(int i=1;i<=n;++i){
        cin >> a;
        parent[i]=a;
    }

    for(int i=1;i<=n;++i){
        if(odw[i]==false)DFS(i,i);
    }

    cout << cykle << 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