Problem p02550 (C++) — buggy submission, verdict: Runtime Error

/*/ Author: kal013 /*/
// #pragma GCC optimize ("O3")
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;
using namespace __gnu_pbds;

template <class T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

template <class key, class value, class cmp = std::less<key>>
using ordered_map =
    tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;
// find_by_order(k)  returns iterator to kth element starting from 0;
// order_of_key(k) returns count of elements strictly smaller than k;

template <class T> using min_heap = priority_queue<T, vector<T>, greater<T>>;

struct custom_hash { // Credits: https://codeforces.com/blog/entry/62393
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
  size_t operator()(pair<int64_t, int64_t> Y) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(Y.first * 31 + Y.second + FIXED_RANDOM);
  }
};

template <class T> ostream &operator<<(ostream &os, vector<T> V) {
  os << "[ ";
  for (auto v : V)
    os << v << " ";
  return os << "]";
}
template <class T> istream &operator>>(istream &is, vector<T> &V) {
  for (auto &e : V)
    is >> e;
  return is;
}

#ifdef __SIZEOF_INT128__
ostream &operator<<(ostream &os, __int128 T) {
  const static long long N = (1'000'000'000'000'000'000);
  if (T < 0) {
    os << '-';
    T *= -1;
  }

  unsigned long long b = T % N;
  T /= N;
  if (T == 0)
    return os << b;
  unsigned long long a = T % N;
  T /= N;
  if (T == 0) {
    os << a;
    __int128 mul = 10;
    int cnt = 0;
    while (mul * b < N && cnt < 17) {
      os << '0';
      mul *= 10;
      ++cnt;
    }
    return os << b;
  }
  os << ((long long)T);

  __int128 mul = 10;
  int cnt = 0;
  while (mul * a < N && cnt < 17) {
    os << '0';
    mul *= 10;
    ++cnt;
  }
  os << a;
  mul = 10;
  cnt = 0;
  while (mul * b < N && cnt < 17) {
    os << '0';
    mul *= 10;
    ++cnt;
  }
  return os << b;
}
istream &operator>>(istream &is, __int128 &T) {
  string U;
  is >> U;
  T = 0;
  size_t pos = 0;
  int mul = 1;
  if (U[pos] == '-') {
    ++pos;
    mul *= -1;
  }
  for (; pos < U.size(); ++pos) {
    T *= 10;
    T += (U[pos] - '0');
  }
  T *= mul;

  return is;
}
#endif
template <class T> ostream &operator<<(ostream &os, set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, unordered_set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, multiset<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, ordered_set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <class L, class R> ostream &operator<<(ostream &os, map<L, R> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}
template <class L, class R, class chash = std::hash<R>>
ostream &operator<<(ostream &os, unordered_map<L, R, chash> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}
template <class L, class R, class chash = std::hash<R>>
ostream &operator<<(ostream &os, gp_hash_table<L, R, chash> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}

#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...) 1
#endif

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

inline int64_t random_long(long long l, long long r) {
  uniform_int_distribution<int64_t> generator(l, r);
  return generator(rng);
}
inline int64_t random_long() {
  uniform_int_distribution<int64_t> generator(LLONG_MIN, LLONG_MAX);
  return generator(rng);
}

/*/---------------------------Defines----------------------/*/
typedef vector<int> vi;
typedef pair<int, int> pii;

#define For(i, n) for (int i = 0; i < (int)n; ++i)
#define Rep(i, n) for (int i = 1; i <= (int)n; ++i)
#define ll long long
#define F first
#define S second
#define pb push_back
#define endl "\\n"
#define all(v) (v).begin(), (v).end()
/*/-----------------------Modular Arithmetic---------------/*/

const int mod = 1e9 + 7;

/*/-----------------------------Code begins----------------------------------/*/

void solve() {

  long long n, x, m;
  cin >> n >> x >> m;
  vector<long long> found(m, -1);

  vector<long long> path;

  long long cur = x;

  while (found[cur] == -1 && path.size() < n) {
    found[cur] = path.size();
    path.push_back(cur);

    cur = (cur * cur) % m;
  }

  long long ans = 0;

  for (auto e : path) {
    ans += e;
  }

  long long rem = n - path.size();
  assert(rem >= 0);
  if (rem == 0) {
    cout << ans << endl;
    return;
  }
  assert(found[cur] != -1);
  vector<long long> ext;
  long long sum = 0;

  for (long long k = found[cur]; k < path.size(); ++k) {
    ext.push_back(path[k]);
    sum += path[k];
  }

  assert(ext.size() > 0);

  long long new_size = ext.size();
  ans += sum * (rem / new_size);

  rem %= new_size;
  for (long long i = 0; i < rem; ++i) {
    ans += ext[i];
  }

  cout << ans << endl;
}
int main() {
  // Use "set_name".max_load_factor(0.25);"set_name".reserve(512); with
  // unordered set Or use gp_hash_table<X,null_type>
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout << fixed << setprecision(25);
  cerr << fixed << setprecision(10);
  auto start = std::chrono::high_resolution_clock::now();
  int t = 1;
  // cin >> t;
  while (t--) {
    solve();
  }
  auto stop = std::chrono::high_resolution_clock::now();
  auto duration =
      std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start);

  // cerr << "Time taken : " << ((long double)duration.count())/((long double)
  // 1e9) <<"s "<< endl;
}

Error: 0

Fixed submission:

/*/ Author: kal013 /*/
// #pragma GCC optimize ("O3")
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;
using namespace __gnu_pbds;

template <class T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

template <class key, class value, class cmp = std::less<key>>
using ordered_map =
    tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;
// find_by_order(k)  returns iterator to kth element starting from 0;
// order_of_key(k) returns count of elements strictly smaller than k;

template <class T> using min_heap = priority_queue<T, vector<T>, greater<T>>;

struct custom_hash { // Credits: https://codeforces.com/blog/entry/62393
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
  size_t operator()(pair<int64_t, int64_t> Y) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(Y.first * 31 + Y.second + FIXED_RANDOM);
  }
};

template <class T> ostream &operator<<(ostream &os, vector<T> V) {
  os << "[ ";
  for (auto v : V)
    os << v << " ";
  return os << "]";
}
template <class T> istream &operator>>(istream &is, vector<T> &V) {
  for (auto &e : V)
    is >> e;
  return is;
}

#ifdef __SIZEOF_INT128__
ostream &operator<<(ostream &os, __int128 T) {
  const static long long N = (1'000'000'000'000'000'000);
  if (T < 0) {
    os << '-';
    T *= -1;
  }

  unsigned long long b = T % N;
  T /= N;
  if (T == 0)
    return os << b;
  unsigned long long a = T % N;
  T /= N;
  if (T == 0) {
    os << a;
    __int128 mul = 10;
    int cnt = 0;
    while (mul * b < N && cnt < 17) {
      os << '0';
      mul *= 10;
      ++cnt;
    }
    return os << b;
  }
  os << ((long long)T);

  __int128 mul = 10;
  int cnt = 0;
  while (mul * a < N && cnt < 17) {
    os << '0';
    mul *= 10;
    ++cnt;
  }
  os << a;
  mul = 10;
  cnt = 0;
  while (mul * b < N && cnt < 17) {
    os << '0';
    mul *= 10;
    ++cnt;
  }
  return os << b;
}
istream &operator>>(istream &is, __int128 &T) {
  string U;
  is >> U;
  T = 0;
  size_t pos = 0;
  int mul = 1;
  if (U[pos] == '-') {
    ++pos;
    mul *= -1;
  }
  for (; pos < U.size(); ++pos) {
    T *= 10;
    T += (U[pos] - '0');
  }
  T *= mul;

  return is;
}
#endif
template <class T> ostream &operator<<(ostream &os, set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, unordered_set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, multiset<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class T> ostream &operator<<(ostream &os, ordered_set<T> S) {
  os << "{ ";
  for (auto s : S)
    os << s << " ";
  return os << "}";
}
template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <class L, class R> ostream &operator<<(ostream &os, map<L, R> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}
template <class L, class R, class chash = std::hash<R>>
ostream &operator<<(ostream &os, unordered_map<L, R, chash> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}
template <class L, class R, class chash = std::hash<R>>
ostream &operator<<(ostream &os, gp_hash_table<L, R, chash> M) {
  os << "{ ";
  for (auto m : M)
    os << "(" << m.first << ":" << m.second << ") ";
  return os << "}";
}

#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
#else
#define trace(...) 1
#endif

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

inline int64_t random_long(long long l, long long r) {
  uniform_int_distribution<int64_t> generator(l, r);
  return generator(rng);
}
inline int64_t random_long() {
  uniform_int_distribution<int64_t> generator(LLONG_MIN, LLONG_MAX);
  return generator(rng);
}

/*/---------------------------Defines----------------------/*/
typedef vector<int> vi;
typedef pair<int, int> pii;

#define For(i, n) for (int i = 0; i < (int)n; ++i)
#define Rep(i, n) for (int i = 1; i <= (int)n; ++i)
#define ll long long
#define F first
#define S second
#define pb push_back
#define endl "\\n"
#define all(v) (v).begin(), (v).end()
/*/-----------------------Modular Arithmetic---------------/*/

const int mod = 1e9 + 7;

/*/-----------------------------Code begins----------------------------------/*/

void solve() {

  long long n, x, m;
  cin >> n >> x >> m;
  vector<int> found(m, -1);

  vector<int> path;

  long long cur = x;

  while (found[cur] == -1 && path.size() < n) {
    found[cur] = path.size();
    path.push_back(cur);

    cur = (cur * cur) % m;
  }

  long long ans = 0;

  for (auto e : path) {
    ans += e;
  }

  long long rem = n - path.size();

  vector<long long> ext;

  for (int k = found[cur]; k < path.size(); ++k) {
    ext.push_back(path[k]);
  }
  long long sum = accumulate(ext.begin(), ext.end(), 0);
  ans += sum * (rem / ext.size());

  rem %= ext.size();

  for (int i = 0; i < rem; ++i) {
    ans += ext[i];
  }

  cout << ans << endl;
}
int main() {
  // Use "set_name".max_load_factor(0.25);"set_name".reserve(512); with
  // unordered set Or use gp_hash_table<X,null_type>
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout << fixed << setprecision(25);
  cerr << fixed << setprecision(10);
  auto start = std::chrono::high_resolution_clock::now();
  int t = 1;
  // cin >> t;
  while (t--) {
    solve();
  }
  auto stop = std::chrono::high_resolution_clock::now();
  auto duration =
      std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start);

  // cerr << "Time taken : " << ((long double)duration.count())/((long double)
  // 1e9) <<"s "<< endl;
}