Submission #1609312

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Source Code Expand

#include "bits/stdc++.h"
#define REP(i,n) for(int i=0;i< (n);i++)
#define REPR(i, n) for(int i = (n);i >= 0;i--)
#define FOR(i, m, n) for(int i = (m);i < (n);i++)
#define FORR(i, m, n) for(int i = (m);i >= (n);i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define ll long long
#define pb(a) push_back(a)
#define ALL(obj) (obj).begin(),(obj).end()

using namespace std;

const int INF = 99999999;
const ll LINF = 9999999999999;

typedef pair<int, int> P;
typedef pair<ll, ll> LP;
int vx[4] = { 0,1,0,-1 };
int vy[4] = { 1,0,-1,0 };

int n,like=0;
vector<int> a;


signed main() {

	std::ios::sync_with_stdio(false);
	std::cin.tie(0);

	cin >> n;

	int tmp;
	REP(i, n) {
		cin >> tmp;
		a.push_back(tmp);
	}

	REP(i, n) {
		if (a[a[i]-1] == i+1) {
			//相思相愛
			like++;
		}
	}

	cout << like / 2 << endl;

	return 0;
}

Submission Info

Judge Result