Submission #7099610

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <functional> // std::function<void(int)>
using namespace std;
#define int long long
#define All(v) (v).begin(),(v).end()
int dy[4] = {-1,0,1,0};
int dx[4] = {0,1,0,-1};
int Dy[8] = {-1,-1,0,1,1,1,0,-1};
int Dx[8] = {0,1,1,1,0,-1,-1,-1};
const int mod = 1000000007;
const int inf = mod*mod;
const int d5 = 111111;
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin>>n;
    int res=0;
    vector<int> a(n);
    for(int i=0;i<n;i++)cin>>a[i];
    for(int i=0;i<n;i++)a[i]--;
    for(int i=0;i<n;i++){
        if(a[a[i]]==i&&a[a[a[i]]]==a[i])res++;
    }
    cout<<res/2<<endl;
}

Submission Info

Judge Result