Submission #891128

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef long double LD;
typedef pair<LD, LD> PLDLD;
typedef pair<char, char> PCC;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define CLR(a) memset((a), 0 ,sizeof(a))
#define ALL(a) a.begin(),a.end()
LL MOD = 1e9+7;
LL INF = 1e17;
double EPS=1.0e-9;
double PI=atan2(0,-1);

int main()
{
    int n;
    cin>>n;
    vector<int> a(n+1);
    FOR(i,1,n+1)
        cin>>a[i];
    int cnt=0;
    FOR(i,1,n+1)
    {
        if(a[a[i]]==i)
            cnt++;
    }
    cout<<(cnt/2)<<endl;
}

Submission Info

Judge Result