Problem p02599 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define ll long long
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INF = 1000000000;
const ll LINF = 1000000000000000000; // 1e18
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const double PI = acos(-1.0);
const double EPS = 1e-10;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
// template<class T> inline void add(T &a, T b){a = ((a+b) % MOD + MOD) % MOD;};

/*  ----------------------- DEBUG FUNCTION ---------------------------- */
#define DUMPOUT cerr
void dump_function() { DUMPOUT << ' '; }
void dump_function(bool a) { DUMPOUT << a; }
void dump_function(int a) { DUMPOUT << a; }
void dump_function(long long a) { DUMPOUT << a; }
void dump_function(char a) { DUMPOUT << a; }
void dump_function(string &a) { DUMPOUT << a; }
void dump_function(double a) { DUMPOUT << a; }
template <class T> void dump_function(const vector<T> &);
template <class T, size_t size> void dump_function(const array<T, size> &);
template <class T, class L> void dump_function(const pair<T, L> &p);
template <class T, size_t size> void dump_function(const T (&)[size]);
template <class T> void dump_function(const vector<T> &a) {
  if (a.empty())
    return;
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
  DUMPOUT << endl;
}
template <class T> void dump_function(const deque<T> &a) {
  if (a.empty())
    return;
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T, size_t size> void dump_function(const array<T, size> &a) {
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T, class L> void dump_function(const pair<T, L> &p) {
  DUMPOUT << '(';
  dump_function(p.first);
  DUMPOUT << ",";
  dump_function(p.second);
  DUMPOUT << ')';
}
template <class T> void dump_function(set<T> &x) {
  for (auto e : x)
    dump_function(e), DUMPOUT << " ";
  DUMPOUT << endl;
}
template <class T> void dump_function(multiset<T> &x) {
  for (auto e : x)
    dump_function(e), DUMPOUT << " ";
  DUMPOUT << endl;
}
template <class T, size_t size> void dump_function(const T (&a)[size]) {
  dump_function(a[0]);
  for (auto i = a; ++i != end(a);) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T> void dump_function(const T &a) { DUMPOUT << a; }
int dump_out() {
  DUMPOUT << '\n';
  return 0;
}
template <class T> int dump_out(const T &t) {
  dump_function(t);
  DUMPOUT << '\n';
  return 0;
}
template <class Head, class... Tail>
int dump_out(const Head &head, const Tail &...tail) {
  dump_function(head);
  DUMPOUT << ' ';
  dump_out(tail...);
  return 0;
}

#ifdef DEBUG_
#define dump(x)                                                                \
  DUMPOUT << #x << ": ";                                                       \
  dump_function(x);                                                            \
  DUMPOUT << endl;
void dumps() {}
template <class T> void dumps(const T &t) {
  dump_function(t);
  DUMPOUT << " ";
}
template <class Head, class... Tail>
void dumps(const Head &head, const Tail &...tail) {
  dump_function(head);
  DUMPOUT << ' ';
  dump_out(tail...);
}
#else
#define dump(x)
template <class... T> void dumps(const T &...) {}
#endif
/*  ----------------------- DEBUG FUNCTION ---------------------------- */

template <int MOD> struct Fp {
  long long val;
  constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};

template <class T> struct BiCoef {
  vector<T> fact_, inv_, finv_;
  constexpr BiCoef() {}
  constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
    init(n);
  }
  constexpr void init(int n) noexcept {
    fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
    int MOD = fact_[0].getmod();
    for (int i = 2; i < n; i++) {
      fact_[i] = fact_[i - 1] * i;
      inv_[i] = -inv_[MOD % i] * (MOD / i);
      finv_[i] = finv_[i - 1] * inv_[i];
    }
  }
  constexpr T com(int n, int k) const noexcept {
    if (n < k || n < 0 || k < 0)
      return 0;
    return fact_[n] * finv_[k] * finv_[n - k];
  }
  constexpr T fact(int n) const noexcept {
    if (n < 0)
      return 0;
    return fact_[n];
  }
  constexpr T inv(int n) const noexcept {
    if (n < 0)
      return 0;
    return inv_[n];
  }
  constexpr T finv(int n) const noexcept {
    if (n < 0)
      return 0;
    return finv_[n];
  }
  constexpr T perm(int n, int k) const noexcept {
    if (n < k || n < 0 || k < 0)
      return 0;
    return fact_[n] * finv_[n - k];
  }
};

using mint = Fp<MOD>;
BiCoef<mint> bc;
// using vec = vector<mint>;
// using mat = vector<vec>;

struct Mo {
  vector<int> left, right, order;
  vector<bool> v;
  vector<int> A;
  vector<int> cnt;
  vector<int> ans;
  int num;
  int width;
  int nl, nr;

  Mo(int n, int q, vector<int> a)
      : width((int)sqrt(n)), order(q), cnt(n, 0), A(a), ans(q), nl(0), nr(0),
        num(0), v(n) {
    iota(begin(order), end(order), 0);
  }

  /* [l, r) */
  void insert(int l, int r) {
    left.push_back(l);
    right.push_back(r);
  }

  /* クエリをソートし、操作を行う */
  void build() {
    assert(left.size() == order.size());
    sort(begin(order), end(order), [&](int a, int b) {
      if (left[a] / width != left[b] / width)
        return left[a] < left[b];
      return right[a] < right[b];
    });
    for (auto idx : order)
      process(idx);
  }

  /* クエリを1つ分進めて, ansに入れる */
  void process(int idx) {
    // if(ptr == order.size()) return (-1);
    // const auto id = order[ptr];
    while (nl > left[idx])
      distribute(--nl);
    while (nr < right[idx])
      distribute(nr++);
    while (nl < left[idx])
      distribute(nl++);
    while (nr > right[idx])
      distribute(--nr);
    ans[idx] = num;
    // return (order[ptr++]);
  }

  inline void distribute(int idx) {
    v[idx].flip();
    if (v[idx])
      add(idx);
    else
      del(idx);
  }

  /* add と delを問題ごとに書く */
  /* add(idx) : A[idx]を区間に新たに加えるとどうなるかを更新する */
  /* del(idx) : A[idx]を区間から除くとどうなるかを更新 */
  void add(int idx) {
    if (cnt[A[idx]]++ == 0)
      ++num;
  }
  void del(int idx) {
    if (--cnt[A[idx]] == 0)
      --num;
  }
};

void solve() {
  int N, Q;
  cin >> N >> Q;
  vector<int> A(N);
  REP(i, N) cin >> A[i];
  Mo mo(N, Q, A);
  REP(i, Q) {
    int l, r;
    cin >> l >> r;
    mo.insert(--l, r);
  }
  mo.build();
  for (auto x : mo.ans)
    cout << x << '\n';
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
  // int T; cin >> T; REP(t,T) solve();
}

Fixed submission:
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define ll long long
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INF = 1000000000;
const ll LINF = 1000000000000000000; // 1e18
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const double PI = acos(-1.0);
const double EPS = 1e-10;

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
// template<class T> inline void add(T &a, T b){a = ((a+b) % MOD + MOD) % MOD;};

/*  ----------------------- DEBUG FUNCTION ---------------------------- */
#define DUMPOUT cerr
void dump_function() { DUMPOUT << ' '; }
void dump_function(bool a) { DUMPOUT << a; }
void dump_function(int a) { DUMPOUT << a; }
void dump_function(long long a) { DUMPOUT << a; }
void dump_function(char a) { DUMPOUT << a; }
void dump_function(string &a) { DUMPOUT << a; }
void dump_function(double a) { DUMPOUT << a; }
template <class T> void dump_function(const vector<T> &);
template <class T, size_t size> void dump_function(const array<T, size> &);
template <class T, class L> void dump_function(const pair<T, L> &p);
template <class T, size_t size> void dump_function(const T (&)[size]);
template <class T> void dump_function(const vector<T> &a) {
  if (a.empty())
    return;
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
  DUMPOUT << endl;
}
template <class T> void dump_function(const deque<T> &a) {
  if (a.empty())
    return;
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T, size_t size> void dump_function(const array<T, size> &a) {
  dump_function(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T, class L> void dump_function(const pair<T, L> &p) {
  DUMPOUT << '(';
  dump_function(p.first);
  DUMPOUT << ",";
  dump_function(p.second);
  DUMPOUT << ')';
}
template <class T> void dump_function(set<T> &x) {
  for (auto e : x)
    dump_function(e), DUMPOUT << " ";
  DUMPOUT << endl;
}
template <class T> void dump_function(multiset<T> &x) {
  for (auto e : x)
    dump_function(e), DUMPOUT << " ";
  DUMPOUT << endl;
}
template <class T, size_t size> void dump_function(const T (&a)[size]) {
  dump_function(a[0]);
  for (auto i = a; ++i != end(a);) {
    DUMPOUT << " ";
    dump_function(*i);
  }
}
template <class T> void dump_function(const T &a) { DUMPOUT << a; }
int dump_out() {
  DUMPOUT << '\n';
  return 0;
}
template <class T> int dump_out(const T &t) {
  dump_function(t);
  DUMPOUT << '\n';
  return 0;
}
template <class Head, class... Tail>
int dump_out(const Head &head, const Tail &...tail) {
  dump_function(head);
  DUMPOUT << ' ';
  dump_out(tail...);
  return 0;
}

#ifdef DEBUG_
#define dump(x)                                                                \
  DUMPOUT << #x << ": ";                                                       \
  dump_function(x);                                                            \
  DUMPOUT << endl;
void dumps() {}
template <class T> void dumps(const T &t) {
  dump_function(t);
  DUMPOUT << " ";
}
template <class Head, class... Tail>
void dumps(const Head &head, const Tail &...tail) {
  dump_function(head);
  DUMPOUT << ' ';
  dump_out(tail...);
}
#else
#define dump(x)
template <class... T> void dumps(const T &...) {}
#endif
/*  ----------------------- DEBUG FUNCTION ---------------------------- */

template <int MOD> struct Fp {
  long long val;
  constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }
  constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }
  constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }
  constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }
  constexpr Fp &operator+=(const Fp &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr Fp &operator-=(const Fp &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr Fp &operator*=(const Fp &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr Fp &operator/=(const Fp &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const Fp &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const Fp &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};

template <class T> struct BiCoef {
  vector<T> fact_, inv_, finv_;
  constexpr BiCoef() {}
  constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
    init(n);
  }
  constexpr void init(int n) noexcept {
    fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
    int MOD = fact_[0].getmod();
    for (int i = 2; i < n; i++) {
      fact_[i] = fact_[i - 1] * i;
      inv_[i] = -inv_[MOD % i] * (MOD / i);
      finv_[i] = finv_[i - 1] * inv_[i];
    }
  }
  constexpr T com(int n, int k) const noexcept {
    if (n < k || n < 0 || k < 0)
      return 0;
    return fact_[n] * finv_[k] * finv_[n - k];
  }
  constexpr T fact(int n) const noexcept {
    if (n < 0)
      return 0;
    return fact_[n];
  }
  constexpr T inv(int n) const noexcept {
    if (n < 0)
      return 0;
    return inv_[n];
  }
  constexpr T finv(int n) const noexcept {
    if (n < 0)
      return 0;
    return finv_[n];
  }
  constexpr T perm(int n, int k) const noexcept {
    if (n < k || n < 0 || k < 0)
      return 0;
    return fact_[n] * finv_[n - k];
  }
};

using mint = Fp<MOD>;
BiCoef<mint> bc;
// using vec = vector<mint>;
// using mat = vector<vec>;

struct Mo {
  vector<int> left, right, order;
  vector<bool> v;
  vector<int> A;
  vector<int> cnt;
  vector<int> ans;
  int num;
  int width;
  int nl, nr;

  Mo(int n, int q, vector<int> a)
      : width((int)sqrt(n)), order(q), cnt(n, 0), A(a), ans(q), nl(0), nr(0),
        num(0), v(n) {
    iota(begin(order), end(order), 0);
  }

  /* [l, r) */
  void insert(int l, int r) {
    left.push_back(l);
    right.push_back(r);
  }

  /* クエリをソートし、操作を行う */
  void build() {
    assert(left.size() == order.size());
    sort(begin(order), end(order), [&](int a, int b) {
      if (left[a] / width != left[b] / width)
        return left[a] < left[b];
      if ((left[a] / width) & 1)
        return right[a] < right[b];
      return right[a] > right[b];
    });
    for (auto idx : order)
      process(idx);
  }

  /* クエリを1つ分進めて, ansに入れる */
  void process(int idx) {
    // if(ptr == order.size()) return (-1);
    // const auto id = order[ptr];
    while (nl > left[idx])
      distribute(--nl);
    while (nr < right[idx])
      distribute(nr++);
    while (nl < left[idx])
      distribute(nl++);
    while (nr > right[idx])
      distribute(--nr);
    ans[idx] = num;
    // return (order[ptr++]);
  }

  inline void distribute(int idx) {
    v[idx].flip();
    if (v[idx])
      add(idx);
    else
      del(idx);
  }

  /* add と delを問題ごとに書く */
  /* add(idx) : A[idx]を区間に新たに加えるとどうなるかを更新する */
  /* del(idx) : A[idx]を区間から除くとどうなるかを更新 */
  void add(int idx) {
    if (cnt[A[idx]]++ == 0)
      ++num;
  }
  void del(int idx) {
    if (--cnt[A[idx]] == 0)
      --num;
  }
};

void solve() {
  int N, Q;
  cin >> N >> Q;
  vector<int> A(N);
  REP(i, N) cin >> A[i];
  Mo mo(N, Q, A);
  REP(i, Q) {
    int l, r;
    cin >> l >> r;
    mo.insert(--l, r);
  }
  mo.build();
  for (auto x : mo.ans)
    cout << x << '\n';
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
  // int T; cin >> T; REP(t,T) solve();
}