755C - PolandBall and Forest - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;

#define endl "\n" ;
#define sort(v) sort(v.begin() , v.end());
#define reverse(v) reverse(v.begin() , v.end());
typedef pair<long long, long long > ii;
typedef vector<long long > vl;
typedef vector<int>vi ;
typedef vector<ii> vii;
typedef long long ll;
typedef  long double ld;

const int  N = 10000 + 5;
int  oo = 100000;
ll const MOD = 1e9 + 7;


int dx[] = { 0, 1, -1,0 };
int dy[] = { 1,0 , 0,-1 };

vi arr[N];
int visited [N];

void dfs(int node ){
    visited[node]=1;
    for (auto child : arr[node]){
        if(!visited[child])dfs(child);
    }
}
int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n ; cin >> n  ;

    for (int i = 1 ; i <= n ; i ++ ){
        int x ; cin >> x ;
        arr[x].push_back(i);
        arr[i].push_back(x);
    }

    int c = 0 ;

    for (int i = 1 ; i <= n ; i ++ ){
        if(!visited[i]){
            c++;
            dfs(i);
        }
    }

    cout << c ;

    return 0;


}