Problem p02840 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// TEMPLATE
// START---------------8<---------------8<---------------8<---------------8<---------------//
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<string> vst;
typedef vector<bool> vb;
typedef vector<ld> vld;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<vector<int>> vvi;
const int INF = (0x7FFFFFFFL);
const ll INFF = (0x7FFFFFFFFFFFFFFFL);
const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int MOD = 1e9 + 7;
const int MODD = 998244353;
const string alphabet = "abcdefghijklmnopqrstuvwxyz";
const double PI = acos(-1.0);
const double EPS = 1e-9;
const string Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
int dx[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
int dy[9] = {0, 1, 0, -1, -1, -1, 1, 1, 0};
#define ln '\n'
#define scnaf scanf
#define sacnf scanf
#define sancf scanf
#define SS(type, ...)                                                          \
  type __VA_ARGS__;                                                            \
  MACRO_VAR_Scan(__VA_ARGS__);
template <typename T> void MACRO_VAR_Scan(T &t) { cin >> t; }
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First &first, Rest &...rest) {
  cin >> first;
  MACRO_VAR_Scan(rest...);
}
#define SV(type, c, n)                                                         \
  vector<type> c(n);                                                           \
  for (auto &i : c)                                                            \
    cin >> i;
#define SVV(type, c, n, m)                                                     \
  vector<vector<type>> c(n, vector<type>(m));                                  \
  for (auto &r : c)                                                            \
    for (auto &i : r)                                                          \
      cin >> i;
template <class T, class U>
ostream &operator<<(ostream &o, const pair<T, U> &j) {
  o << "{" << j.first << ", " << j.second << "}";
  return o;
}
template <class T, class U>
ostream &operator<<(ostream &o, const map<T, U> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const set<T> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const multiset<T> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const vector<T> &j) {
  o << "{";
  for (int i = 0; i < (int)j.size(); ++i)
    o << (i > 0 ? ", " : "") << j[i];
  o << "}";
  return o;
}
inline int print(void) {
  cout << endl;
  return 0;
}
template <class Head> int print(Head &&head) {
  cout << head;
  print();
  return 0;
}
template <class Head, class... Tail> int print(Head &&head, Tail &&...tail) {
  cout << head << " ";
  print(forward<Tail>(tail)...);
  return 0;
}
#ifdef LOCAL
inline int dump(void) {
  cerr << endl;
  return 0;
}
template <class Head> int dump(Head &&head) {
  cerr << head;
  dump();
  return 0;
}
template <class Head, class... Tail> int dump(Head &&head, Tail &&...tail) {
  cerr << head << " ";
  dump(forward<Tail>(tail)...);
  return 0;
}
#define debug(...)                                                             \
  do {                                                                         \
    cerr << __LINE__ << ":	" << #__VA_ARGS__ << " = ";                  \
    dump(__VA_ARGS__);                                                         \
  } while (0)
#define ER(x) cerr << #x << " = " << (x) << endl;
#define ERV(v)                                                                 \
  {                                                                            \
    cerr << #v << " : ";                                                       \
    for (const auto &xxx : v) {                                                \
      cerr << xxx << " ";                                                      \
    }                                                                          \
    cerr << "\n";                                                              \
  }
#else
#define dump(...)
#define debug(...)
#define ER(x)
#define ERV(v)
#endif
template <typename T> void PA(T &a) {
  int ASIZE = sizeof(a) / sizeof(a[0]);
  for (int ii = 0; ii < ASIZE; ++ii) {
    cout << a[ii] << " \n"[ii == ASIZE - 1];
  }
}
template <typename T> void PV(T &v) {
  int VSIZE = v.size();
  for (int ii = 0; ii < VSIZE; ++ii) {
    cout << v[ii] << " \n"[ii == VSIZE - 1];
  }
}
inline int YES(bool x) {
  cout << ((x) ? "YES" : "NO") << endl;
  return 0;
}
inline int Yes(bool x) {
  cout << ((x) ? "Yes" : "No") << endl;
  return 0;
}
inline int yes(bool x) {
  cout << ((x) ? "yes" : "no") << endl;
  return 0;
}
inline int yES(bool x) {
  cout << ((x) ? "yES" : "nO") << endl;
  return 0;
}
inline int Yay(bool x) {
  cout << ((x) ? "Yay!" : ":(") << endl;
  return 0;
}
template <typename A, typename B> void sankou(bool x, A a, B b) {
  cout << ((x) ? (a) : (b)) << endl;
}
#define _overload3(_1, _2, _3, name, ...) name
#define _REP(i, n) REPI(i, 0, n)
#define REPI(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define REP(...) _overload3(__VA_ARGS__, REPI, _REP, )(__VA_ARGS__)
#define _RREP(i, n) RREPI(i, n, 0)
#define RREPI(i, a, b) for (ll i = ll(a); i >= ll(b); --i)
#define RREP(...) _overload3(__VA_ARGS__, RREPI, _RREP, )(__VA_ARGS__)
#define EACH(e, v) for (auto &e : v)
#define PERM(v)                                                                \
  sort((v).begin(), (v).end());                                                \
  for (bool c##p = 1; c##p; c##p = next_permutation((v).begin(), (v).end()))
#define ADD(a, b) a = (a + ll(b)) % MOD
#define MUL(a, b) a = (a * ll(b)) % MOD
inline ll MOP(ll x, ll n, ll m = MOD) {
  ll r = 1;
  while (n > 0) {
    if (n & 1)
      (r *= x) %= m;
    (x *= x) %= m;
    n >>= 1;
  }
  return r;
}
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
inline ll POW(ll a, ll b) {
  ll c = 1ll;
  do {
    if (b & 1)
      c *= 1ll * a;
    a *= 1ll * a;
  } while (b >>= 1);
  return c;
}
template <typename T, typename A, typename B>
inline bool between(T x, A a, B b) {
  return ((a <= x) && (x < b));
}
template <class T> inline T sqr(T x) { return x * x; }
template <typename A, typename B> inline bool chmax(A &a, const B &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename A, typename B> inline bool chmin(A &a, const B &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define tmax(x, y, z) max((x), max((y), (z)))
#define tmin(x, y, z) min((x), min((y), (z)))
#define PB emplace_back
#define MP make_pair
#define MT make_tuple
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define SORT(v) sort((v).begin(), (v).end())
#define RSORT(v) sort((v).rbegin(), (v).rend())
#define EXIST(s, e) (find((s).begin(), (s).end(), (e)) != (s).end())
#define EXISTST(s, c) (((s).find(c)) != string::npos)
#define POSL(x, val) (lower_bound(x.begin(), x.end(), val) - x.begin())
#define POSU(x, val) (upper_bound(x.begin(), x.end(), val) - x.begin())
#define GEQ(x, val) (int)(x).size() - POSL((x), (val))
#define GREATER(x, val) (int)(x).size() - POSU((x), (val))
#define LEQ(x, val) POSU((x), (val))
#define LESS(x, val) POSL((x), (val))
#define SZV(a) int((a).size())
#define SZA(a) sizeof(a) / sizeof(a[0])
#define ZERO(a) memset(a, 0, sizeof(a))
#define MINUS(a) memset(a, 0xff, sizeof(a))
#define MEMINF(a) memset(a, 0x3f, sizeof(a))
#define FILL(a, b) memset(a, b, sizeof(a))
#define UNIQUE(v)                                                              \
  sort((v).begin(), (v).end());                                                \
  (v).erase(unique((v).begin(), (v).end()), (v).end())
struct abracadabra {
  abracadabra() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);
    cerr << fixed << setprecision(5);
  };
} ABRACADABRA;

// TEMPLATE
// END---------------8<---------------8<---------------8<---------------8<---------------//

struct SegmentMap : public map<int_fast64_t, int_fast64_t> {
  bool flagToMergeAdjacentSegment;
  SegmentMap(bool flagToMergeAdjacentSegment = true)
      : flagToMergeAdjacentSegment(flagToMergeAdjacentSegment) {}
  auto get(int_fast64_t p) const {
    auto it = upper_bound(p);
    if (it == begin() or (--it)->second < p)
      return end();
    return it;
  }
  void insert(int_fast64_t l, int_fast64_t r) {
    auto itl = upper_bound(l),
         itr = upper_bound(r + flagToMergeAdjacentSegment);
    if (itl != begin()) {
      if ((--itl)->second < l - flagToMergeAdjacentSegment)
        ++itl;
    }
    if (itl != itr) {
      l = min(l, itl->first);
      r = max(r, prev(itr)->second);
      erase(itl, itr);
    }
    (*this)[l] = r;
  }
  void remove(int_fast64_t l, int_fast64_t r) {
    auto itl = upper_bound(l), itr = upper_bound(r);
    if (itl != begin()) {
      if ((--itl)->second < l)
        ++itl;
    }
    if (itl == itr)
      return;
    int tl = min(l, itl->first), tr = max(r, prev(itr)->second);
    erase(itl, itr);
    if (tl < l)
      (*this)[tl] = l - 1;
    if (r < tr)
      (*this)[r + 1] = tr;
  }
  bool same(int_fast64_t p, int_fast64_t q) const {
    const auto &&it = get(p);
    return it != end() and it->first <= q and q <= it->second;
  }
};

/*
・SegmentMap
[備考] 区間をmapで管理するやつ
[注意] 以下で扱う区間は全て閉区間
[使用例]
SegmentMap mp(flag);    // flagがtrueなら, [l, c]と[c + 1, r]をマージする
mp.get(p);              // pを含む区間を返す(存在しないならmp.end())
mp.insert(l, r);        // 閉区間[l, r]を追加する
mp.remove(l, r);        // 閉区間[l, r]を取り除く
mp.same(p, q);          // 2点p, qが同じ区間にあればtrue
*/

/*
    正負で対称 奇数のときは0の分(サンプル3)
    S-TじゃなくてSの通り数で良くない？
*/

signed main() {

  SS(int, N, X, D);

  if (D == 0) {
    // print(N + 1);
    assert(0);
    return 0;
  }

  map<int, SegmentMap> mps;

  REP(i, N + 1) {
    ll bas = i * X;
    ll frm = i * (i - 1) / 2;
    ll len = i * N - (i * i - 1);
    mps[bas % D].insert(bas / D + frm, bas / D + frm + len - 1);
  }

  ll res = 0;
  EACH(mp, mps) {
    EACH(e, mp.second) {
      ll l, r;
      tie(l, r) = e;
      // print(l, r);
      res += r - l + 1;
    }
  }
  print(res);

  // cerr << "D == 0のときの書いた？" << endl;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// TEMPLATE
// START---------------8<---------------8<---------------8<---------------8<---------------//
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<string> vst;
typedef vector<bool> vb;
typedef vector<ld> vld;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<vector<int>> vvi;
const int INF = (0x7FFFFFFFL);
const ll INFF = (0x7FFFFFFFFFFFFFFFL);
const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int MOD = 1e9 + 7;
const int MODD = 998244353;
const string alphabet = "abcdefghijklmnopqrstuvwxyz";
const double PI = acos(-1.0);
const double EPS = 1e-9;
const string Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
int dx[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
int dy[9] = {0, 1, 0, -1, -1, -1, 1, 1, 0};
#define ln '\n'
#define scnaf scanf
#define sacnf scanf
#define sancf scanf
#define SS(type, ...)                                                          \
  type __VA_ARGS__;                                                            \
  MACRO_VAR_Scan(__VA_ARGS__);
template <typename T> void MACRO_VAR_Scan(T &t) { cin >> t; }
template <typename First, typename... Rest>
void MACRO_VAR_Scan(First &first, Rest &...rest) {
  cin >> first;
  MACRO_VAR_Scan(rest...);
}
#define SV(type, c, n)                                                         \
  vector<type> c(n);                                                           \
  for (auto &i : c)                                                            \
    cin >> i;
#define SVV(type, c, n, m)                                                     \
  vector<vector<type>> c(n, vector<type>(m));                                  \
  for (auto &r : c)                                                            \
    for (auto &i : r)                                                          \
      cin >> i;
template <class T, class U>
ostream &operator<<(ostream &o, const pair<T, U> &j) {
  o << "{" << j.first << ", " << j.second << "}";
  return o;
}
template <class T, class U>
ostream &operator<<(ostream &o, const map<T, U> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const set<T> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const multiset<T> &j) {
  o << "{";
  for (auto t = j.begin(); t != j.end(); ++t)
    o << (t != j.begin() ? ", " : "") << *t;
  o << "}";
  return o;
}
template <class T> ostream &operator<<(ostream &o, const vector<T> &j) {
  o << "{";
  for (int i = 0; i < (int)j.size(); ++i)
    o << (i > 0 ? ", " : "") << j[i];
  o << "}";
  return o;
}
inline int print(void) {
  cout << endl;
  return 0;
}
template <class Head> int print(Head &&head) {
  cout << head;
  print();
  return 0;
}
template <class Head, class... Tail> int print(Head &&head, Tail &&...tail) {
  cout << head << " ";
  print(forward<Tail>(tail)...);
  return 0;
}
#ifdef LOCAL
inline int dump(void) {
  cerr << endl;
  return 0;
}
template <class Head> int dump(Head &&head) {
  cerr << head;
  dump();
  return 0;
}
template <class Head, class... Tail> int dump(Head &&head, Tail &&...tail) {
  cerr << head << " ";
  dump(forward<Tail>(tail)...);
  return 0;
}
#define debug(...)                                                             \
  do {                                                                         \
    cerr << __LINE__ << ":	" << #__VA_ARGS__ << " = ";                  \
    dump(__VA_ARGS__);                                                         \
  } while (0)
#define ER(x) cerr << #x << " = " << (x) << endl;
#define ERV(v)                                                                 \
  {                                                                            \
    cerr << #v << " : ";                                                       \
    for (const auto &xxx : v) {                                                \
      cerr << xxx << " ";                                                      \
    }                                                                          \
    cerr << "\n";                                                              \
  }
#else
#define dump(...)
#define debug(...)
#define ER(x)
#define ERV(v)
#endif
template <typename T> void PA(T &a) {
  int ASIZE = sizeof(a) / sizeof(a[0]);
  for (int ii = 0; ii < ASIZE; ++ii) {
    cout << a[ii] << " \n"[ii == ASIZE - 1];
  }
}
template <typename T> void PV(T &v) {
  int VSIZE = v.size();
  for (int ii = 0; ii < VSIZE; ++ii) {
    cout << v[ii] << " \n"[ii == VSIZE - 1];
  }
}
inline int YES(bool x) {
  cout << ((x) ? "YES" : "NO") << endl;
  return 0;
}
inline int Yes(bool x) {
  cout << ((x) ? "Yes" : "No") << endl;
  return 0;
}
inline int yes(bool x) {
  cout << ((x) ? "yes" : "no") << endl;
  return 0;
}
inline int yES(bool x) {
  cout << ((x) ? "yES" : "nO") << endl;
  return 0;
}
inline int Yay(bool x) {
  cout << ((x) ? "Yay!" : ":(") << endl;
  return 0;
}
template <typename A, typename B> void sankou(bool x, A a, B b) {
  cout << ((x) ? (a) : (b)) << endl;
}
#define _overload3(_1, _2, _3, name, ...) name
#define _REP(i, n) REPI(i, 0, n)
#define REPI(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define REP(...) _overload3(__VA_ARGS__, REPI, _REP, )(__VA_ARGS__)
#define _RREP(i, n) RREPI(i, n, 0)
#define RREPI(i, a, b) for (ll i = ll(a); i >= ll(b); --i)
#define RREP(...) _overload3(__VA_ARGS__, RREPI, _RREP, )(__VA_ARGS__)
#define EACH(e, v) for (auto &e : v)
#define PERM(v)                                                                \
  sort((v).begin(), (v).end());                                                \
  for (bool c##p = 1; c##p; c##p = next_permutation((v).begin(), (v).end()))
#define ADD(a, b) a = (a + ll(b)) % MOD
#define MUL(a, b) a = (a * ll(b)) % MOD
inline ll MOP(ll x, ll n, ll m = MOD) {
  ll r = 1;
  while (n > 0) {
    if (n & 1)
      (r *= x) %= m;
    (x *= x) %= m;
    n >>= 1;
  }
  return r;
}
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
inline ll POW(ll a, ll b) {
  ll c = 1ll;
  do {
    if (b & 1)
      c *= 1ll * a;
    a *= 1ll * a;
  } while (b >>= 1);
  return c;
}
template <typename T, typename A, typename B>
inline bool between(T x, A a, B b) {
  return ((a <= x) && (x < b));
}
template <class T> inline T sqr(T x) { return x * x; }
template <typename A, typename B> inline bool chmax(A &a, const B &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename A, typename B> inline bool chmin(A &a, const B &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
#define tmax(x, y, z) max((x), max((y), (z)))
#define tmin(x, y, z) min((x), min((y), (z)))
#define PB emplace_back
#define MP make_pair
#define MT make_tuple
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define SORT(v) sort((v).begin(), (v).end())
#define RSORT(v) sort((v).rbegin(), (v).rend())
#define EXIST(s, e) (find((s).begin(), (s).end(), (e)) != (s).end())
#define EXISTST(s, c) (((s).find(c)) != string::npos)
#define POSL(x, val) (lower_bound(x.begin(), x.end(), val) - x.begin())
#define POSU(x, val) (upper_bound(x.begin(), x.end(), val) - x.begin())
#define GEQ(x, val) (int)(x).size() - POSL((x), (val))
#define GREATER(x, val) (int)(x).size() - POSU((x), (val))
#define LEQ(x, val) POSU((x), (val))
#define LESS(x, val) POSL((x), (val))
#define SZV(a) int((a).size())
#define SZA(a) sizeof(a) / sizeof(a[0])
#define ZERO(a) memset(a, 0, sizeof(a))
#define MINUS(a) memset(a, 0xff, sizeof(a))
#define MEMINF(a) memset(a, 0x3f, sizeof(a))
#define FILL(a, b) memset(a, b, sizeof(a))
#define UNIQUE(v)                                                              \
  sort((v).begin(), (v).end());                                                \
  (v).erase(unique((v).begin(), (v).end()), (v).end())
struct abracadabra {
  abracadabra() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);
    cerr << fixed << setprecision(5);
  };
} ABRACADABRA;

// TEMPLATE
// END---------------8<---------------8<---------------8<---------------8<---------------//

struct SegmentMap : public map<int_fast64_t, int_fast64_t> {
  bool flagToMergeAdjacentSegment;
  SegmentMap(bool flagToMergeAdjacentSegment = true)
      : flagToMergeAdjacentSegment(flagToMergeAdjacentSegment) {}
  auto get(int_fast64_t p) const {
    auto it = upper_bound(p);
    if (it == begin() or (--it)->second < p)
      return end();
    return it;
  }
  void insert(int_fast64_t l, int_fast64_t r) {
    auto itl = upper_bound(l),
         itr = upper_bound(r + flagToMergeAdjacentSegment);
    if (itl != begin()) {
      if ((--itl)->second < l - flagToMergeAdjacentSegment)
        ++itl;
    }
    if (itl != itr) {
      l = min(l, itl->first);
      r = max(r, prev(itr)->second);
      erase(itl, itr);
    }
    (*this)[l] = r;
  }
  void remove(int_fast64_t l, int_fast64_t r) {
    auto itl = upper_bound(l), itr = upper_bound(r);
    if (itl != begin()) {
      if ((--itl)->second < l)
        ++itl;
    }
    if (itl == itr)
      return;
    int tl = min(l, itl->first), tr = max(r, prev(itr)->second);
    erase(itl, itr);
    if (tl < l)
      (*this)[tl] = l - 1;
    if (r < tr)
      (*this)[r + 1] = tr;
  }
  bool same(int_fast64_t p, int_fast64_t q) const {
    const auto &&it = get(p);
    return it != end() and it->first <= q and q <= it->second;
  }
};

/*
・SegmentMap
[備考] 区間をmapで管理するやつ
[注意] 以下で扱う区間は全て閉区間
[使用例]
SegmentMap mp(flag);    // flagがtrueなら, [l, c]と[c + 1, r]をマージする
mp.get(p);              // pを含む区間を返す(存在しないならmp.end())
mp.insert(l, r);        // 閉区間[l, r]を追加する
mp.remove(l, r);        // 閉区間[l, r]を取り除く
mp.same(p, q);          // 2点p, qが同じ区間にあればtrue
*/

/*
    正負で対称 奇数のときは0の分(サンプル3)
    S-TじゃなくてSの通り数で良くない？
*/

signed main() {

  SS(int, N, X, D);

  if (D == 0) {
    if (X == 0)
      print(1);
    else
      print(N + 1);
    return 0;
  }

  map<int, SegmentMap> mps;

  REP(i, N + 1) {
    ll bas = i * X;
    ll frm = i * (i - 1) / 2;
    ll len = i * N - (i * i - 1);
    mps[bas % D].insert(bas / D + frm, bas / D + frm + len - 1);
  }

  ll res = 0;
  EACH(mp, mps) {
    EACH(e, mp.second) {
      ll l, r;
      tie(l, r) = e;
      // print(l, r);
      res += r - l + 1;
    }
  }
  print(res);

  // cerr << "D == 0のときの書いた？" << endl;
}