Problem p02599 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = b - 1; i >= a; i--)
#define repl(i, a, b) for (long long i = a; i < b; i++)
#define rrepl(i, a, b) for (long long i = b - 1; i >= a; i--)
#define ALL(a) a.begin(), a.end()
using pii = pair<int, int>;
using piii = pair<pii, int>;
using pll = pair<long long, long long>;
using plll = pair<pll, long long>;
// #pragma GCC optimize("Ofast")
// #define _GLIBCXX_DEBUG
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define pb push_back
#define mp make_pair
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define isSquare(x) (sqrt(x) * sqrt(x) == x)
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
};
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
};
inline void in(void) { return; }
template <typename First, typename... Rest>
void in(First &first, Rest &...rest) {
  cin >> first;
  in(rest...);
  return;
}
inline void out(void) {
  cout << "\\n";
  return;
}
template <typename First, typename... Rest>
void out(First first, Rest... rest) {
  cout << first << " ";
  out(rest...);
  return;
}
const double EPS = 1e-9;
const int mod = 1e9 + 7;
// const int mod = 998244353;
const int INF = 1e9;
const long long INFLL = 1e18;
void iosetup() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}
template <class T> vector<T> make_vec(size_t a) { return vector<T>(a); }
template <class T, class... Ts> auto make_vec(size_t a, Ts... ts) {
  return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T>
pair<S, T> operator*(const pair<S, T> &s, const S &t) {
  return pair<S, T>(s.first * t, s.second * t);
}
template <typename T> void Exit(T first) {
  cout << first << endl;
  exit(0);
};
template <int mod> struct ModInt {
  unsigned x;
  ModInt() : x(0) {}
  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }
  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  static int get_mod() { return mod; }
};
using modint = ModInt<mod>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const pii dxy[4] = {pii(1, 0), pii(0, 1), pii(-1, 0), pii(0, -1)};

//----------------------- edit from here ---------------------------------

template <typename T> struct BinaryIndexedTree {
  vector<T> data;

  BinaryIndexedTree(int sz) { data.assign(++sz, 0); }

  T sum(int k) {
    T ret = 0;
    for (++k; k > 0; k -= k & -k)
      ret += data[k];
    return (ret);
  }

  void add(int k, T x) {
    for (++k; k < data.size(); k += k & -k)
      data[k] += x;
  }
};

// BinaryIndexedTree< int > bit(n);
// sum(k) : [0,k]の合計を求める
// add(k, x) : 要素kに値xを加える

int main() {
  iosetup();
  int n, Q;
  cin >> n;
  cin >> Q;
  vector<int> A(n);
  vector<int> lastAppeard(n + 1, -1);

  for (int i = 0; i < n; i++) {
    cin >> A[i];
  }
  // rep(i, 0, n) lastAppeard[A[i]] = i;
  vector<piii> query;
  rep(i, 0, Q) {
    int l, r;
    cin >> l >> r;
    query.emplace_back(pii(l, r), i);
  }
  sort(ALL(query),
       [](piii a, piii b) { return a.first.second < b.first.second; });
  BinaryIndexedTree<int> bit(n + 1);
  // rep(i, 1, n + 1) if(lastAppeard[i] != -1){
  //     bit.add(i, 1);
  // }
  int pre = -1;
  vector<int> ans(Q);
  rep(i, 0, Q) {
    auto lr = query[i].first;
    auto idx = query[i].second;
    int l = lr.first, r = lr.second;
    l--, r--;
    if (pre != r) {
      rep(j, pre + 1, r + 1) {
        if (lastAppeard[A[j]] != -1)
          bit.add(lastAppeard[A[j]], -1);
        bit.add(j, 1);
        lastAppeard[A[j]] = j;
      }
      pre = r;
    }
    ans[idx] = bit.sum(r) - bit.sum(l - 1);
  }
  rep(i, 0, Q) cout << ans[i] << endl;

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits.h>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define rrep(i, a, b) for (int i = b - 1; i >= a; i--)
#define repl(i, a, b) for (long long i = a; i < b; i++)
#define rrepl(i, a, b) for (long long i = b - 1; i >= a; i--)
#define ALL(a) a.begin(), a.end()
using pii = pair<int, int>;
using piii = pair<pii, int>;
using pll = pair<long long, long long>;
using plll = pair<pll, long long>;
// #pragma GCC optimize("Ofast")
// #define _GLIBCXX_DEBUG
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define pb push_back
#define mp make_pair
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define isSquare(x) (sqrt(x) * sqrt(x) == x)
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
};
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
};
inline void in(void) { return; }
template <typename First, typename... Rest>
void in(First &first, Rest &...rest) {
  cin >> first;
  in(rest...);
  return;
}
inline void out(void) {
  cout << "\\n";
  return;
}
template <typename First, typename... Rest>
void out(First first, Rest... rest) {
  cout << first << " ";
  out(rest...);
  return;
}
const double EPS = 1e-9;
const int mod = 1e9 + 7;
// const int mod = 998244353;
const int INF = 1e9;
const long long INFLL = 1e18;
void iosetup() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}
template <class T> vector<T> make_vec(size_t a) { return vector<T>(a); }
template <class T, class... Ts> auto make_vec(size_t a, Ts... ts) {
  return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}
template <class S, class T>
pair<S, T> operator*(const pair<S, T> &s, const S &t) {
  return pair<S, T>(s.first * t, s.second * t);
}
template <typename T> void Exit(T first) {
  cout << first << endl;
  exit(0);
};
template <int mod> struct ModInt {
  unsigned x;
  ModInt() : x(0) {}
  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  ModInt &operator+=(const ModInt &p) {
    if ((x += p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator-=(const ModInt &p) {
    if ((x += mod - p.x) >= mod)
      x -= mod;
    return *this;
  }
  ModInt &operator*=(const ModInt &p) {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }
  ModInt operator-() const { return ModInt(-x); }
  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
  bool operator==(const ModInt &p) const { return x == p.x; }
  bool operator!=(const ModInt &p) const { return x != p.x; }
  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while (n > 0) {
      if (n & 1)
        ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }
  friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  static int get_mod() { return mod; }
};
using modint = ModInt<mod>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const pii dxy[4] = {pii(1, 0), pii(0, 1), pii(-1, 0), pii(0, -1)};

//----------------------- edit from here ---------------------------------

struct Mo {
  using ADD = function<void(int)>;
  using DEL = function<void(int)>;
  using REM = function<void(int)>;

  int width;
  vector<int> left, right, order;
  vector<bool> v;

  Mo(int N, int Q) : width((int)sqrt(N)), order(Q), v(N) {
    iota(begin(order), end(order), 0);
  }

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

  void run(const ADD &add, const DEL &del, const REM &rem) {
    assert(left.size() == order.size());
    sort(begin(order), end(order), [&](int a, int b) {
      int ablock = left[a] / width, bblock = left[b] / width;
      if (ablock != bblock)
        return ablock < bblock;
      if (ablock & 1)
        return right[a] < right[b];
      return right[a] > right[b];
    });
    int nl = 0, nr = 0;
    auto push = [&](int idx) {
      v[idx].flip();
      if (v[idx])
        add(idx);
      else
        del(idx);
    };
    for (auto idx : order) {
      while (nl > left[idx])
        push(--nl);
      while (nr < right[idx])
        push(nr++);
      while (nl < left[idx])
        push(nl++);
      while (nr > right[idx])
        push(--nr);
      rem(idx);
    }
  }
};

int main() {
  int N, Q;
  cin >> N;
  cin >> Q;
  vector<int> A(N);
  for (int i = 0; i < N; i++) {
    cin >> A[i];
  }
  vector<int> f(1000001);
  Mo mo(N, Q);
  for (int i = 0; i < Q; i++) {
    int l, r;
    cin >> l >> r;
    mo.add(--l, r);
  }
  int ret = 0;
  auto add = [&](int idx) {
    if (f[A[idx]]++ == 0)
      ret++;
  };
  auto del = [&](int idx) {
    if (f[A[idx]]-- == 1)
      --ret;
  };
  vector<int> ans(Q);
  auto rem = [&](int idx) { ans[idx] = ret; };
  mo.run(add, del, rem);
  for (int i = 0; i < Q; i++) {
    cout << ans[i] << "\\n";
  }
}