Problem p02684 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")

using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
typedef long long ll;
#define rep(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define REP(i, num, n) for (int i = num, i##_len = (n); i < i##_len; ++i)
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 (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
#define print(x) (cout << (x) << endl)
#define pb push_back
#define mp make_pair
#define sz(x) int(x.size())
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
#define fs first
#define sc second
// 多倍長
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>
using boost::rational;
using boost::multiprecision::cpp_int;

const int INF = 1e9;
const ll LLINF = 1e16;
const ll MOD = 1e9 + 7;
template <class T> inline void add(T &a, T b) {
  a = ((a + b) % MOD + MOD) % MOD;
};

template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }

template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

// 指定した文字cが文字列に何文字入ってるか
ll stringcount(string s, char c) { return count(s.cbegin(), s.cend(), c); }

// 割り算の切り上げ処理
template <typename T> T rp(T a, T b) { return (a + b - 1) / b; }

// 桁和
template <typename T> T digsum(T n) {
  T res = 0;
  while (n > 0) {
    res += n % 10;
    n /= 10;
  }
  return res;
}

// 回文判定
bool kai(string s) {
  string t{s};
  reverse(begin(t), end(t));
  return s == t;
}

using pint = pair<int, int>;
using pll = pair<ll, ll>;

vector<string> split(const string &s, char delim) {
  vector<string> elems;
  string item;
  for (char ch : s) {
    if (ch == delim) {
      if (!item.empty())
        elems.push_back(item);
      item.clear();
    } else {
      item += ch;
    }
  }
  if (!item.empty())
    elems.push_back(item);
  return elems;
}

ll dp[60][205000];
int main(void) {
  cout.tie(0);
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  ll n, k;
  cin >> n >> k;
  rep(i, n) {
    cin >> dp[0][i];
    dp[0][i]--;
  }
  rep(i, 59) {
    rep(j, n) { dp[i + 1][j] = dp[i][dp[i][j]]; }
  }
  int v = 0;
  for (int i = 59; i >= 0; --i) {
    ll l = 1LL << i;
    if (l <= k) {
      v = dp[i][v];
      k -= l;
    }
  }
  print(v + 1);
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")

using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
typedef long long ll;
#define rep(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define REP(i, num, n) for (int i = num, i##_len = (n); i < i##_len; ++i)
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 (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
#define print(x) (cout << (x) << endl)
#define pb push_back
#define mp make_pair
#define sz(x) int(x.size())
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
#define fs first
#define sc second
// 多倍長
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/rational.hpp>
using boost::rational;
using boost::multiprecision::cpp_int;

const int INF = 1e9;
const ll LLINF = 1e16;
const ll MOD = 1e9 + 7;
template <class T> inline void add(T &a, T b) {
  a = ((a + b) % MOD + MOD) % MOD;
};

template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }

template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

// 指定した文字cが文字列に何文字入ってるか
ll stringcount(string s, char c) { return count(s.cbegin(), s.cend(), c); }

// 割り算の切り上げ処理
template <typename T> T rp(T a, T b) { return (a + b - 1) / b; }

// 桁和
template <typename T> T digsum(T n) {
  T res = 0;
  while (n > 0) {
    res += n % 10;
    n /= 10;
  }
  return res;
}

// 回文判定
bool kai(string s) {
  string t{s};
  reverse(begin(t), end(t));
  return s == t;
}

using pint = pair<int, int>;
using pll = pair<ll, ll>;

vector<string> split(const string &s, char delim) {
  vector<string> elems;
  string item;
  for (char ch : s) {
    if (ch == delim) {
      if (!item.empty())
        elems.push_back(item);
      item.clear();
    } else {
      item += ch;
    }
  }
  if (!item.empty())
    elems.push_back(item);
  return elems;
}

ll dp[60][205000];
int main(void) {
  cout.tie(0);
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  ll n, k;
  cin >> n >> k;
  rep(i, n) {
    cin >> dp[0][i];
    dp[0][i]--;
  }
  rep(i, 60) {
    rep(j, n) { dp[i + 1][j] = dp[i][dp[i][j]]; }
  }
  int v = 0;
  for (int i = 59; i >= 0; --i) {
    ll l = 1LL << i;
    if (l <= k) {
      v = dp[i][v];
      k -= l;
    }
  }
  print(v + 1);
}