Submission #890800

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Source Code Expand

#include <bits/stdc++.h>

/* -------------------------------- Template -------------------------------- */

#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()

using namespace std;

using ll = long long;
using ld = long double;

template <typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }

template<typename T> T inf() { assert(false); }
template<> constexpr int inf<int>() { return 1e9; }
template<> constexpr ll inf<ll>() { return 1e18; }
template<> constexpr ld inf<ld>() { return 1e30; }

/* -------------------------------- Library -------------------------------- */

/* ---------------------------------- Main ---------------------------------- */

int main() {
  int N;
  cin >> N;
  vector<int> a(N);
  int res = 0;
  REP(i,N) {
    cin >> a[i];
    --a[i];
  }
  REP(i,N) {
    if (a[a[i]] == i) ++res;
  }
  cout << res / 2 << endl;
  return 0;
}

Submission Info

Judge Result