Submission #890973

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Source Code Expand

#include <iostream>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <algorithm>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <functional>
#include <complex>
#include <bitset>
#include <numeric>
using namespace std;

typedef long long LL;
#define REP(i,n) for(int (i)=0; (i)<(n) ;++(i))
#define REPN(i,a,n) FOR((i),(a),(a)+(n))
#define FOR(i,a,b) for(int (i)=(a); (i)<(b) ;++(i))
#define PB push_back
#define MP make_pair
#define OUT(a) cout<<(a)<<endl;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,a[100010]={},ans=0;

    cin >> n;
    REP(i,n){
        cin >> a[i+1];
    }

    REPN(i,1,n){
        if(a[a[i]]==i) ans++;
    }

    cout<< ans/2 << endl;

    return 0;
}

Submission Info

Judge Result