Submission #891402

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Source Code Expand

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007
#define MOD 1000000007
#define EPS 1e-10
#define MAX_N 100100
#define MAX_M 100100

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;
typedef pair<P, char> PC;
typedef pair<ll, string> PLS;

int n;
int a[100100];
bool f[100100];

int main(){
	int ans = 0;
	cin >> n;
	fill(f, f + n, 1);
	REP(i, n){
		cin >> a[i];
		a[i]--;
	}
	REP(i, n){
		if (f[i]){
			if (a[a[i]] == i){
				ans++;
				f[i] = 0;
				f[a[i]] = 0;
			}
		}
	}
	cout << ans << endl;
}

Submission Info

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