Submission #890920

---

Source Code Expand

#include <bits/stdc++.h>

using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> Vi;
//typedef tuple<int, int, int> T;
#define FOR(i,s,x) for(int i=s;i<(int)(x);i++)
#define REP(i,x) FOR(i,0,x)
#define ALL(c) c.begin(), c.end()
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

const int dr[4] = {-1, 0, 1, 0};
const int dc[4] = {0, 1, 0, -1};

int main() {
  // use scanf in CodeForces!
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N; cin >> N;
  vector<int> A(N);
  REP(i, N) {
    cin >> A[i];
    A[i]--;
  }

  int ans = 0;
  REP(i, N) {
    if (A[A[i]] == i) ans++;
  }
  cout << ans / 2 << endl;
  return 0;
}

Submission Info

Judge Result