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

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>

#define int ll
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define reps(i, n) for (int i = 1; i <= (n); ++i)
#define repd(i, n) for (int i = (n)-1; i >= 0; --i)
#define repds(i, n) for (int i = (n); i > 0; --i)
#define loop(i, x, n) for (int i = (x); i < (n); ++i)
#define loops(i, x, n) for (int i = (x); i <= (n); ++i)
#define loopd(i, x, n) for (int i = (x); i > (n); --i)
#define loopds(i, x, n) for (int i = (x); i >= (n); --i)
#define itrep(i, a) for (auto i = begin(a); i != end(a); ++i)
#define itrepd(i, a) for (auto i = rbegin(a); i != rend(a); ++i)
#define each(i, x) for (auto &&i : x)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
template <class T>
using priority_queuel = priority_queue<T, vector<T>, greater<T>>;
constexpr ll inf = static_cast<ll>(1e18);
constexpr int iinf = static_cast<int>(1e9);
constexpr double dinf = 1e10;
constexpr ld ldinf = 1e18;
constexpr double eps = 1e-9;
ll mod = static_cast<ll>(1e9 + 7);
template <class T> constexpr int sz(const T &a) { return (int)a.size(); }
template <class T> constexpr T pow2(const T a) { return a * a; }
template <class T, class... Args> constexpr void mins(T &a, Args... args) {
  a = min<T>({a, args...});
}
template <class T, class... Args> constexpr void maxs(T &a, Args... args) {
  a = max<T>({a, args...});
}

template <class F> class FixPoint : private F {
public:
  explicit constexpr FixPoint(F &&f) : F(std::forward<F>(f)) {}
  template <class... Args>
  constexpr decltype(auto) operator()(Args &&...args) const {
    return F::operator()(*this, std::forward<Args>(args)...);
  }
};

template <class F> constexpr decltype(auto) funcs(F &&f) {
  return FixPoint<F>{std::forward<F>(f)};
}

template <class T> std::vector<T> vecs(int n, T &&val) {
  return std::vector<T>(std::forward<int>(n), std::forward<T>(val));
}

template <class... Args> decltype(auto) vecs(int n, Args &&...args) {
  return std::vector<decltype(vecs(std::forward<Args>(args)...))>(
      std::forward<int>(n), vecs(std::forward<Args>(args)...));
}

template <class V, class T> void fill(V &x, const T &val) { x = val; }

template <class V, class T> void fill(vector<V> &vec, const T &val) {
  for (auto &&v : vec)
    fill(v, val);
}

void solve() {
  int n, k;
  cin >> n >> k;
  auto log_v = log2(k) + 2;
  auto val = vecs(n, 63, int());
  rep(i, n) {
    int a;
    cin >> a;
    --a;
    val[i][0] = a;
  }

  rep(j, log_v - 1) rep(i, n) val[i][j + 1] = val[val[i][j]][j];
  int pos = 0;
  repd(i, log_v) {
    if ((k >> i) & 1)
      pos = val[pos][i];
  }

  cout << pos + 1 << '\\n';
}

signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  solve();
  cout.flush();
  return 0;
}


Error: 0

Fixed submission:

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>

#define int ll
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define reps(i, n) for (int i = 1; i <= (n); ++i)
#define repd(i, n) for (int i = (n)-1; i >= 0; --i)
#define repds(i, n) for (int i = (n); i > 0; --i)
#define loop(i, x, n) for (int i = (x); i < (n); ++i)
#define loops(i, x, n) for (int i = (x); i <= (n); ++i)
#define loopd(i, x, n) for (int i = (x); i > (n); --i)
#define loopds(i, x, n) for (int i = (x); i >= (n); --i)
#define itrep(i, a) for (auto i = begin(a); i != end(a); ++i)
#define itrepd(i, a) for (auto i = rbegin(a); i != rend(a); ++i)
#define each(i, x) for (auto &&i : x)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
template <class T>
using priority_queuel = priority_queue<T, vector<T>, greater<T>>;
constexpr ll inf = static_cast<ll>(1e18);
constexpr int iinf = static_cast<int>(1e9);
constexpr double dinf = 1e10;
constexpr ld ldinf = 1e18;
constexpr double eps = 1e-9;
ll mod = static_cast<ll>(1e9 + 7);
template <class T> constexpr int sz(const T &a) { return (int)a.size(); }
template <class T> constexpr T pow2(const T a) { return a * a; }
template <class T, class... Args> constexpr void mins(T &a, Args... args) {
  a = min<T>({a, args...});
}
template <class T, class... Args> constexpr void maxs(T &a, Args... args) {
  a = max<T>({a, args...});
}

template <class F> class FixPoint : private F {
public:
  explicit constexpr FixPoint(F &&f) : F(std::forward<F>(f)) {}
  template <class... Args>
  constexpr decltype(auto) operator()(Args &&...args) const {
    return F::operator()(*this, std::forward<Args>(args)...);
  }
};

template <class F> constexpr decltype(auto) funcs(F &&f) {
  return FixPoint<F>{std::forward<F>(f)};
}

template <class T> std::vector<T> vecs(int n, T &&val) {
  return std::vector<T>(std::forward<int>(n), std::forward<T>(val));
}

template <class... Args> decltype(auto) vecs(int n, Args &&...args) {
  return std::vector<decltype(vecs(std::forward<Args>(args)...))>(
      std::forward<int>(n), vecs(std::forward<Args>(args)...));
}

template <class V, class T> void fill(V &x, const T &val) { x = val; }

template <class V, class T> void fill(vector<V> &vec, const T &val) {
  for (auto &&v : vec)
    fill(v, val);
}

void solve() {
  int n, k;
  cin >> n >> k;
  auto log_v = log2(k) + 2;
  auto val = vecs(n, log_v, int());
  rep(i, n) {
    int a;
    cin >> a;
    --a;
    val[i][0] = a;
  }

  rep(j, log_v - 1) rep(i, n) val[i][j + 1] = val[val[i][j]][j];
  int pos = 0;
  repd(i, log_v) {
    if ((k >> i) & 1)
      pos = val[pos][i];
  }

  cout << pos + 1 << endl;
}

signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  solve();
  cout.flush();
  return 0;
}