Submission #891050

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Source Code Expand

#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <set>
#include <vector>
#include <map>
#include <cmath>
#include <algorithm>
#include <memory.h>
#include <string>
#include <sstream>
#include <cstdlib>
#include <ctime>
#include <cassert>

using namespace std;

typedef long long LL;
typedef pair<int,int> PII;

#define MP make_pair
#define PB push_back
#define FF first
#define SS second

#define FORN(i, n) for (int i = 0; i <  (int)(n); i++)
#define FOR1(i, n) for (int i = 1; i <= (int)(n); i++)
#define FORD(i, n) for (int i = (int)(n) - 1; i >= 0; i--)

#define DEBUG(X) { cout << #X << " = " << (X) << endl; }
#define PR0(A,n) { cout << #A << " = "; FORN(_,n) cout << A[_] << ' '; cout << endl; }

#define MOD 1000000007
#define INF 2000000000

int GLL(LL& x) {
    return scanf("%lld", &x);
}

int GI(int& x) {
    return scanf("%d", &x);
}

const int MAXN = 100010;
int a[MAXN];

int n;

int main() {
    GI(n);

    FOR1(i, n) {
        GI(a[i]);
    }

    int res = 0;

    FOR1(i, n) {
        res += (a[a[i]] == i);
    }
    
    cout << res / 2 << "\n";

    return 0;
}

Submission Info

Judge Result