Submission #891294

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Source Code Expand

#include <stdio.h>
#include <stdlib.h>
#include<iostream>
#include <vector>
#include <map>
#include <list>
#include <queue>
#include <string.h>
#include <string>
#include <limits.h>
#include <algorithm>
#include <set>
#include <ctime>
#include <cmath>
#include <assert.h>
#include <stack>
using namespace std;
#define SZ(x) ((int)(x).size())
#define rep(i,a,n) for (int i=a; i<(int)n; i++)
#define per(i,n,a) for (int i=n; i>=a; i--)
#define hk push_back
#define pk pop_back
#define mp make_pair
#define PI 3.141592653589793
#define clr(a) memset(a, 0, sizeof(a))
#define clr1(a) memset(a, -1, sizeof(a))
#define c_false ios_base::sync_with_stdio(false); cin.tie(0)
typedef vector<int> VI;
typedef vector< pair<int, int> > VIP;
typedef vector< pair<int, pair<int, int> > > VIPP;
typedef vector<string> VS;
typedef vector <double> VD;
typedef vector <bool> VB;
typedef long long ll;
#define MAX_V 1000
const ll mod = 1000000007;
ll powmod(ll a, ll b) {
	ll res = 1; a %= mod; for (; b; b >>= 1){ if (b & 1)res = res*a%mod; a = a*a%mod; }return res;
}

int n, a[100005];

int main()
{
	c_false;
	cin >> n;
	rep(i, 1, n + 1) cin >> a[i];
	int ans = 0;
	rep(i, 1, n + 1) {
		int j = a[i], k = a[j];
		if (i == k) ans++;
	}
	ans /= 2;
	cout << ans << endl;

	return 0;
}

Submission Info

Judge Result