Submission #1173045

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Source Code Expand

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#define ll long long
int main() {
	cin.tie(0); ios::sync_with_stdio(false);
	ll N, a; cin >> N >> a;
	string k; cin >> k;
	vector<ll> b(N + 1, 0);
	for (int i = 1; i <= N;i++)cin >> b[i];
	vector<ll> m(N + 1, -1);
	m[b[a]] = 1;
	ll i = 1; i++;
	ll now = b[b[a]];

	ll d1, d2;

	//cout << b[a] << " " << m[b[a]] << " " << 1 << endl;
	while (true) {

		//cout << now << " " << m[now] << " " << i << endl;

		if (m[now] != -1) {
			d1 = m[now];
			d2 = i - m[now];
			break;
		}
		else {
			m[now] = i;
			now = b[now];
			i++;
		}
	}

	int k_num = atoi(k.c_str());
	if (k.size() < 8 && k_num < d1) {
		int now = a;
		for (int i = 0; i < k_num; i++) {
			now = b[now];
		}
		cout << now << endl;
	}
	else {
		int k_mod_C = 0;
		for (int i = 0; i < k.size();i++) {
			k_mod_C = (k_mod_C * 10 + (k[i] - '0')) % d2;
		}
		k_mod_C += d1*d2;
		k_mod_C -= d1;
		k_mod_C %= d2;

		for (int i = 0; i < k_mod_C;i++) {
			now = b[now];
		}
		cout << now << endl;
	}
}

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