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

#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#include <iostream>

#include <deque>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include <algorithm>
#include <bitset>
#include <functional>
#include <memory>
#include <string>
#include <tuple>
#include <utility>
using namespace std;

#define lowbit(x) ((x) & -(x))
#define lson l, mid, id << 1
#define rson mid + 1, r, id << 1 | 1
#define ls id << 1
#define rs id << 1 | 1
#define MID(l, r) ((l) + (((r) - (l)) >> 1))
#define fi first
#define se second
#define mk make_pair
#define mt make_tuple
#define pb push_back
#define epb emplace_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

using LL = long long;
// using LL = __int64;
using pii = pair<int, int>;
using pdd = pair<double, double>;
using pLL = pair<LL, LL>;

const int INF = 0x3f3f3f3f;
const LL LINF = 0x3f3f3f3f3f3f3f3f;
const double DINF = 1e100;
const double pi = acos(-1.0);
const double eps = 1e-7;
const int e5 = 100000;          // 1e5
const int e6 = 1000000;         // 1e6;
const int MOD_1e9 = 1000000007; // 1e9 + 7
const int MOD_998 = 998244353;
const int MOD = MOD_1e9;

template <typename T> inline void get_min(T &x, T y) {
  if (y < x)
    x = y;
}
template <typename T> inline void get_max(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void get_unique(vector<T> &vec) {
  sort(all(vec));
  vec.erase(unique(all(vec)), vec.end());
}

inline int sig(double x) { return x < -eps ? -1 : eps < x; }
LL fp(LL a, LL n, LL mod = MOD) {
  if (n < 0)
    a = fp(a, mod - 2, mod), n = -n;
  LL res = 1;
  for (; n; n >>= 1, a = a * a % mod)
    if (n & 1)
      res = res * a % mod;
  return res;
}

template <int mod> class Mint {
private:
  int x;

public:
  Mint() : x(0) {}
  Mint(int _x) : x(_x) {
    if (x < 0 || x >= mod)
      x %= mod;
    if (x < 0)
      x += mod;
  }
  Mint(LL _x) {
    if (_x < 0 || _x >= mod)
      _x %= mod;
    if (_x < 0)
      _x += mod;
    x = _x;
  }
  Mint operator()() { return x; }
  Mint operator-() const { return Mint(x == 0 ? x : mod - x); }
  Mint operator+(const Mint &rhs) const {
    return Mint(x + rhs.x >= mod ? x + rhs.x - mod : x + rhs.x);
  }
  Mint operator-(const Mint &rhs) const {
    return Mint(x - rhs.x < 0 ? x - rhs.x + mod : x - rhs.x);
  }
  Mint operator*(const Mint &rhs) const { return Mint((LL)x * rhs.x % mod); }
  Mint operator/(const Mint &rhs) const {
    return Mint((LL)x * fp(rhs.x, -1, mod) % mod);
  }
  bool operator==(const Mint &rhs) const { return x == rhs.x; }
  bool operator!=(const Mint &rhs) const { return x != rhs.x; }
  Mint &operator+=(const Mint &rhs) {
    x += rhs.x;
    if (x >= mod)
      x -= mod;
    return *this;
  }
  Mint &operator-=(const Mint &rhs) {
    x -= rhs.x;
    if (x < 0)
      x += mod;
    return *this;
  }
  Mint &operator*=(const Mint &rhs) {
    x = (LL)x * rhs.x % mod;
    return *this;
  }
  Mint &operator/=(const Mint &rhs) {
    x = (LL)x * fp(rhs.x, -1, mod) % mod;
    return *this;
  }
  friend ostream &operator<<(ostream &out, const Mint &rhs) {
    return out << to_string(rhs.x);
  }
  Mint inv() { return Mint(fp(x, -1, mod)); }
  Mint pow(int k) { return Mint(fp(x, k, mod)); }
};

class fast_reader {
private:
  int buff_size;
  char *buff_ptr;
  char *ptr;
  char *tail;
  bool is_open;
  fast_reader(const fast_reader &) = delete;
  fast_reader &operator=(const fast_reader &) = delete;

  inline bool is_digit() const { return '0' <= *ptr && *ptr <= '9'; }
  inline bool is_blank() const {
    return *ptr == ' ' || *ptr == '\\n' || *ptr == '\\t' || *ptr == '\\0';
  }
  template <typename T> inline void read_i(T &x) {
    bool f = false;
    x = 0;
    while (ptr < tail && !is_digit()) {
      if (*ptr == '-')
        f = true;
      ptr++;
    }
    while (ptr < tail && is_digit()) {
      x = (x << 1) + (x << 3) + (*ptr & 0xf);
      ptr++;
    }
    if (f)
      x = -x;
  }
  template <typename T> inline void read_f(T &x) {
    static char t_buff[1 << 6];
    read(t_buff);
    x = atof(t_buff);
  }

public:
  fast_reader()
      : buff_size(0), buff_ptr(nullptr), ptr(nullptr), tail(nullptr),
        is_open(false) {}
  ~fast_reader() {
    if (is_open)
      free(buff_ptr);
  }
  template <typename T> fast_reader &operator>>(T &x) {
    read(x);
    return *this;
  }

  inline void open_alter(int _base_size = 1 << 24) // 2^24B = 16MB
  {
    if (is_open)
      throw runtime_error("fast reader is reopened!");

    int input_size = 0;
    int call_size = _base_size;
    buff_ptr = (char *)malloc(call_size);
    input_size += fread(buff_ptr, 1, call_size, stdin);
    while (feof(stdin) == 0) {
      int recall_size = call_size;
      buff_ptr = (char *)realloc(buff_ptr, call_size + recall_size);
      tail = buff_ptr + call_size;
      input_size += fread(tail, 1, recall_size, stdin);
      call_size += recall_size;
    }
    buff_ptr = (char *)realloc(buff_ptr, input_size);
    ptr = buff_ptr;
    tail = buff_ptr + input_size;
    buff_size = input_size;
    is_open = true;
  }

  template <typename T, typename... Args>
  inline void read(T &x, Args &...args) {
    read(x);
    read(args...);
  }
  inline void read(int &x) { read_i(x); }
  inline void read(unsigned &x) { read_i(x); }
  inline void read(long long &x) { read_i(x); }
  inline void read(unsigned long long &x) { read_i(x); }
  inline void read(float &x) { read_f(x); }
  inline void read(double &x) { read_f(x); }
  inline void read(char *str) {
    while (ptr < tail && is_blank())
      ptr++;
    while (ptr < tail && !is_blank())
      *str = *ptr++, str++;
    *str = '\\0';
  }
  inline void read(string &s) {
    while (ptr < tail && is_blank())
      ptr++;
    char *pre = ptr;
    while (ptr < tail && !is_blank())
      ptr++;
    s = std::move(
        string(pre, ptr)); // C++11 #include<utility> -> move : return a rvalue
  }

  inline bool is_end() {
    while (ptr < tail && is_blank())
      ptr++;
    return ptr >= tail;
  }
} reader;

const int maxn = (int)1e5 + 5;
const int maxm = (int)5e6 + 5;

void work() {
  LL n;
  int x, m;
  reader >> n >> x >> m;
  vector<int> a(m * 2, -1);
  vector<int> vis(m + 1, -1);
  a[0] = x;
  vis[a[0]] = 0;
  int len, cir;
  for (int i = 1; i < m * 2; i++) {
    a[i] = (LL)a[i - 1] * a[i - 1] % m;
    if (vis[a[i]] != -1) {
      len = vis[a[i]];
      cir = i - len;
      break;
    }
    vis[a[i]] = i;
  }
  //    cout <<len <<" " <<cir <<endl;

  //    for(int i = 0; i < len + cir + 5; i++) cout <<a[i] <<" "; cout <<endl;

  if (n <= len) {
    LL sum = 0;
    for (int i = 0; i < n; i++)
      sum += a[i];
    cout << sum << endl;
  } else {
    LL suml = 0, sumc = 0;
    for (int i = len; i < len + cir; i++)
      sumc += a[i];
    for (int i = 0; i < len; i++)
      suml += a[i];

    LL d = (n - len) / cir;
    int r = (n - len) % cir;

    LL part = 0;
    for (int i = len; i < len + r; i++)
      part += a[i];

    cout << suml + d * sumc + part << endl;
  }

  //    LL sum = 0;
  //    for(int i = 0; i < len; i++) sum += a[i];
  //
  //    LL d = n / len;
  //    int r = n % len;
  //
  //    LL sum2 = 0;
  //    for(int i = 0; i < r; i++) sum2 += a[i];
  //
  //    cout <<sum * d + sum2 <<endl;
}

int main() {
#ifdef yukihana0416
  freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#endif // yukihana0416
  reader.open_alter(1 << 24);

  int tc = 1;
  //    reader >> tc;
  for (int ca = 1; ca <= tc; ca++) {
    //        printf("Case #%d: ", ca);
    //        printf("Case #%d:\\n", ca);
    work();
  }
  return 0;
}


Error: 0

Fixed submission:

#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#include <iostream>

#include <deque>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include <algorithm>
#include <bitset>
#include <functional>
#include <memory>
#include <string>
#include <tuple>
#include <utility>
using namespace std;

#define lowbit(x) ((x) & -(x))
#define lson l, mid, id << 1
#define rson mid + 1, r, id << 1 | 1
#define ls id << 1
#define rs id << 1 | 1
#define MID(l, r) ((l) + (((r) - (l)) >> 1))
#define fi first
#define se second
#define mk make_pair
#define mt make_tuple
#define pb push_back
#define epb emplace_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

using LL = long long;
// using LL = __int64;
using pii = pair<int, int>;
using pdd = pair<double, double>;
using pLL = pair<LL, LL>;

const int INF = 0x3f3f3f3f;
const LL LINF = 0x3f3f3f3f3f3f3f3f;
const double DINF = 1e100;
const double pi = acos(-1.0);
const double eps = 1e-7;
const int e5 = 100000;          // 1e5
const int e6 = 1000000;         // 1e6;
const int MOD_1e9 = 1000000007; // 1e9 + 7
const int MOD_998 = 998244353;
const int MOD = MOD_1e9;

template <typename T> inline void get_min(T &x, T y) {
  if (y < x)
    x = y;
}
template <typename T> inline void get_max(T &x, T y) {
  if (x < y)
    x = y;
}
template <typename T> inline void get_unique(vector<T> &vec) {
  sort(all(vec));
  vec.erase(unique(all(vec)), vec.end());
}

inline int sig(double x) { return x < -eps ? -1 : eps < x; }
LL fp(LL a, LL n, LL mod = MOD) {
  if (n < 0)
    a = fp(a, mod - 2, mod), n = -n;
  LL res = 1;
  for (; n; n >>= 1, a = a * a % mod)
    if (n & 1)
      res = res * a % mod;
  return res;
}

template <int mod> class Mint {
private:
  int x;

public:
  Mint() : x(0) {}
  Mint(int _x) : x(_x) {
    if (x < 0 || x >= mod)
      x %= mod;
    if (x < 0)
      x += mod;
  }
  Mint(LL _x) {
    if (_x < 0 || _x >= mod)
      _x %= mod;
    if (_x < 0)
      _x += mod;
    x = _x;
  }
  Mint operator()() { return x; }
  Mint operator-() const { return Mint(x == 0 ? x : mod - x); }
  Mint operator+(const Mint &rhs) const {
    return Mint(x + rhs.x >= mod ? x + rhs.x - mod : x + rhs.x);
  }
  Mint operator-(const Mint &rhs) const {
    return Mint(x - rhs.x < 0 ? x - rhs.x + mod : x - rhs.x);
  }
  Mint operator*(const Mint &rhs) const { return Mint((LL)x * rhs.x % mod); }
  Mint operator/(const Mint &rhs) const {
    return Mint((LL)x * fp(rhs.x, -1, mod) % mod);
  }
  bool operator==(const Mint &rhs) const { return x == rhs.x; }
  bool operator!=(const Mint &rhs) const { return x != rhs.x; }
  Mint &operator+=(const Mint &rhs) {
    x += rhs.x;
    if (x >= mod)
      x -= mod;
    return *this;
  }
  Mint &operator-=(const Mint &rhs) {
    x -= rhs.x;
    if (x < 0)
      x += mod;
    return *this;
  }
  Mint &operator*=(const Mint &rhs) {
    x = (LL)x * rhs.x % mod;
    return *this;
  }
  Mint &operator/=(const Mint &rhs) {
    x = (LL)x * fp(rhs.x, -1, mod) % mod;
    return *this;
  }
  friend ostream &operator<<(ostream &out, const Mint &rhs) {
    return out << to_string(rhs.x);
  }
  Mint inv() { return Mint(fp(x, -1, mod)); }
  Mint pow(int k) { return Mint(fp(x, k, mod)); }
};

class fast_reader {
private:
  int buff_size;
  char *buff_ptr;
  char *ptr;
  char *tail;
  bool is_open;
  fast_reader(const fast_reader &) = delete;
  fast_reader &operator=(const fast_reader &) = delete;

  inline bool is_digit() const { return '0' <= *ptr && *ptr <= '9'; }
  inline bool is_blank() const {
    return *ptr == ' ' || *ptr == '\\n' || *ptr == '\\t' || *ptr == '\\0';
  }
  template <typename T> inline void read_i(T &x) {
    bool f = false;
    x = 0;
    while (ptr < tail && !is_digit()) {
      if (*ptr == '-')
        f = true;
      ptr++;
    }
    while (ptr < tail && is_digit()) {
      x = (x << 1) + (x << 3) + (*ptr & 0xf);
      ptr++;
    }
    if (f)
      x = -x;
  }
  template <typename T> inline void read_f(T &x) {
    static char t_buff[1 << 6];
    read(t_buff);
    x = atof(t_buff);
  }

public:
  fast_reader()
      : buff_size(0), buff_ptr(nullptr), ptr(nullptr), tail(nullptr),
        is_open(false) {}
  ~fast_reader() {
    if (is_open)
      free(buff_ptr);
  }
  template <typename T> fast_reader &operator>>(T &x) {
    read(x);
    return *this;
  }

  inline void open_alter(int _base_size = 1 << 24) // 2^24B = 16MB
  {
    if (is_open)
      throw runtime_error("fast reader is reopened!");

    int input_size = 0;
    int call_size = _base_size;
    buff_ptr = (char *)malloc(call_size);
    input_size += fread(buff_ptr, 1, call_size, stdin);
    while (feof(stdin) == 0) {
      int recall_size = call_size;
      buff_ptr = (char *)realloc(buff_ptr, call_size + recall_size);
      tail = buff_ptr + call_size;
      input_size += fread(tail, 1, recall_size, stdin);
      call_size += recall_size;
    }
    buff_ptr = (char *)realloc(buff_ptr, input_size);
    ptr = buff_ptr;
    tail = buff_ptr + input_size;
    buff_size = input_size;
    is_open = true;
  }

  template <typename T, typename... Args>
  inline void read(T &x, Args &...args) {
    read(x);
    read(args...);
  }
  inline void read(int &x) { read_i(x); }
  inline void read(unsigned &x) { read_i(x); }
  inline void read(long long &x) { read_i(x); }
  inline void read(unsigned long long &x) { read_i(x); }
  inline void read(float &x) { read_f(x); }
  inline void read(double &x) { read_f(x); }
  inline void read(char *str) {
    while (ptr < tail && is_blank())
      ptr++;
    while (ptr < tail && !is_blank())
      *str = *ptr++, str++;
    *str = '\\0';
  }
  inline void read(string &s) {
    while (ptr < tail && is_blank())
      ptr++;
    char *pre = ptr;
    while (ptr < tail && !is_blank())
      ptr++;
    s = std::move(
        string(pre, ptr)); // C++11 #include<utility> -> move : return a rvalue
  }

  inline bool is_end() {
    while (ptr < tail && is_blank())
      ptr++;
    return ptr >= tail;
  }
} reader;

const int maxn = (int)1e5 + 5;
const int maxm = (int)5e6 + 5;

void work() {
  LL n;
  int x, m;
  reader >> n >> x >> m;
  vector<int> a(m, -1);
  vector<int> vis(m + 1, -1);
  a[0] = x;
  vis[a[0]] = 0;
  int len, cir;
  for (int i = 1; i < m; i++) {
    a[i] = (LL)a[i - 1] * a[i - 1] % m;
    if (vis[a[i]] != -1) {
      len = vis[a[i]];
      cir = i - len;
      break;
    }
    vis[a[i]] = i;
  }
  //    cout <<len <<" " <<cir <<endl;

  //    for(int i = 0; i < len + cir + 5; i++) cout <<a[i] <<" "; cout <<endl;

  if (n <= len) {
    LL sum = 0;
    for (int i = 0; i < n; i++)
      sum += a[i];
    cout << sum << endl;
  } else {
    LL suml = 0, sumc = 0;
    for (int i = len; i < len + cir; i++)
      sumc += a[i];
    for (int i = 0; i < len; i++)
      suml += a[i];

    LL d = (n - len) / cir;
    int r = (n - len) % cir;

    LL part = 0;
    for (int i = len; i < len + r; i++)
      part += a[i];

    cout << suml + d * sumc + part << endl;
  }

  //    LL sum = 0;
  //    for(int i = 0; i < len; i++) sum += a[i];
  //
  //    LL d = n / len;
  //    int r = n % len;
  //
  //    LL sum2 = 0;
  //    for(int i = 0; i < r; i++) sum2 += a[i];
  //
  //    cout <<sum * d + sum2 <<endl;
}

int main() {
#ifdef yukihana0416
  freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#endif // yukihana0416
  reader.open_alter(1 << 24);

  int tc = 1;
  //    reader >> tc;
  for (int ca = 1; ca <= tc; ca++) {
    //        printf("Case #%d: ", ca);
    //        printf("Case #%d:\\n", ca);
    work();
  }
  return 0;
}