Submission #891387

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define watch(a) { cout << #a << " = " << a << endl; }
template<class T1, class T2> inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); }
template<class T1, class T2> inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); }

typedef long long ll;
int const inf = 1<<29;

int main() {
  string s, t;
  int a, b, c, x, y, z, N;
    
  cin >> N;
  vector<int> vs(N + 1);

  REP(i, 1, N + 1) { cin >> vs[i]; }

  int ans = 0;

//  REP(i, 1, N + 1) {    cout << vs[i] << ", " << vs[vs[i]] << endl;  }cout << endl;

  REP(i, 1, N + 1) {
    ans += i == vs[vs[i]];
  }

  cout << ans / 2 << endl;
  
  return 0;
}

Submission Info

Judge Result