Submission #1417487

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <functional>
#include <cstdlib>
#include <sstream>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <complex>
#include <vector>
#include <bitset>
#include <cstdio>
#include <cmath>
#include <time.h>
#include <tuple>
#define all(c) ((c).begin(),(c).end())
#define rall(c) ((c).rbegin(),(c).rend())
#define ll long long
#define fi first
#define se second
#define inf (999999999)
using namespace std;
const ll MOD = 1e9 + 7;
const double PI = acos(-1.0);
//---------------------------------------------------------------------------------------------//
int n;
int a[100000];
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i]; a[i]--;
	}
	int ans = 0;
	for (int i = 0; i < n; i++) {
		if (a[i] == inf)continue;
		if (a[a[i]] == i) {
			a[a[i]] = inf;
			a[i] = inf;
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}

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