Submission #27383641

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Source Code Expand

#include <algorithm>
#include <bits/stdc++.h>
#include <cmath>
#include <iostream>
#include <map>
#include <math.h>
#include <set>
#include <string>
#include <tuple>
#include <vector>
using namespace std;

#define rep(i, o) for (int i = 0; i < (o); ++i)
#define REP(i, a, b) for (int i = (int)(a); (i) < (int)(b); i++)
#define NUM 1e5

typedef long long ll;
typedef unsigned long long ull;

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll c, ll d) { return c / gcd(c, d) * d; }

const int MOD = 1000000007;

template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}

template <class T>
bool chmin(T &a, const T &b)
{
    if (a > b)
    {
        a = b;
        return 1;
    }
    return 0;
}


int main() {
    ll n, x;
    cin >> n >> x, x--;

    vector<int> a(n);
    rep(i, n) {
      cin >> a[i]; a[i]--;
    }

    map<int, bool> known;
    int ans = 0;
    rep(i, n) {
      if (known[x] != true) {
        known[x] = true;
        x = a[x];
        ans++;
        //cout << x << " " << ans << endl;
      }
    }
    cout << ans << endl;
    return 0;
}

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