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

#include <algorithm>
#include <array>
#include <assert.h>
#include <bitset>
#include <climits>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define LEN(x) (long long)(x.size())
#define FOR(i, a, n) for (int i = (a); i < (n); ++i)
#define FOE(i, a) for (auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_COUNT(bit) (__builtin_popcount(bit))

typedef long long LL;
template <typename T> std::vector<T> make_v(size_t a) {
  return std::vector<T>(a);
}
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return std::vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
} // C++14
template <typename T, typename V>
typename std::enable_if<std::is_class<T>::value == 0>::type fill_v(T &t,
                                                                   const V &v) {
  t = v;
}
template <typename T, typename V>
typename std::enable_if<std::is_class<T>::value != 0>::type fill_v(T &t,
                                                                   const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
template <class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
void print() { std::cout << std::endl; }
template <class Head, class... Tail> void print(Head &&head, Tail &&...tail) {
  std::cout << head;
  if (sizeof...(tail) != 0) {
    std::cout << " ";
  }
  print(std::forward<Tail>(tail)...);
}
template <class T> void print(std::vector<T> &v) {
  for (auto &a : v) {
    std::cout << a;
    if (&a != &v.back()) {
      std::cout << " ";
    }
  }
  std::cout << std::endl;
}
template <class T> void print(std::vector<std::vector<T>> &vv) {
  for (auto &v : vv) {
    print(v);
  }
}
void debug() { std::cerr << std::endl; }
template <class Head, class... Tail> void debug(Head &&head, Tail &&...tail) {
  std::cerr << head;
  if (sizeof...(tail) != 0) {
    std::cerr << " ";
  }
  print(std::forward<Tail>(tail)...);
}
template <class T> void debug(std::vector<T> &v) {
  for (auto &a : v) {
    std::cerr << a;
    if (&a != &v.back()) {
      std::cerr << " ";
    }
  }
  std::cerr << std::endl;
}
template <class T> void debug(std::vector<std::vector<T>> &vv) {
  for (auto &v : vv) {
    print(v);
  }
}
inline bool inside(long long y, long long x, long long H, long long W) {
  return 0 <= y and y < H and 0 <= x and x < W;
}
template <class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
template <class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) {
  return abs(x1 - x2) + abs(y1 - y2);
}
template <typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }
bool is_bit_on(const unsigned long long bit, const unsigned int i) {
  return (bit >> i) & 1u;
}
unsigned long long bit_set(const unsigned long long bit, const unsigned int i,
                           const unsigned int b) {
  assert(b == 0 or b == 1);
  if (b == 0) {
    return bit & ~(1ull << i);
  } else {
    return bit | (1ull << i);
  }
}

// 初項s交差d長さnの数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
  return n * (2 * s + (n - 1) * d) / 2;
}

// xが2の階乗かどうか判定
bool is_power_of_two(long long x) { return !(x & (x - 1)); }

long long gcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}

long long gcd(std::vector<long long> &v) {
  long long ans = v[0];
  for (int i = 1; i < (int)v.size(); ++i) {
    ans = gcd(ans, v[i]);
  }
  return ans;
}

long long lcm(long long a, long long b) {
  long long g = gcd(a, b);
  return a / g * b;
}

const int INF = 1u << 30u; // 1,073,741,824
const long long LINF = 1ull << 60u;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};
const std::vector<int> dy4 = {0, 1, 0, -1}, dx4 = {1, 0, -1, 0};
const std::vector<int> dy8 = {0, -1, 0, 1, 1, -1, -1, 1},
                       dx8 = {1, 0, -1, 0, 1, 1, -1, -1};

template <class T = long long> class FenwickTree {
public:
  const int n;
  std::vector<T> v;

  FenwickTree(int n) : n(n) { this->v.assign(n + 1, 0); }

  T access(int i) { return this->sum(i, i + 1); }

  // sum(v[0, i))
  T sum(int i) {
    assert(0 <= i && i <= this->n);

    T s = 0;
    i -= 1;
    while (i >= 0) {
      s += this->v[i];
      i = (i & (i + 1)) - 1;
    }
    return s;
  }

  // sum(v[left, right))
  T sum(int left, int right) {
    assert(left <= right);
    return this->sum(right) - this->sum(left);
  }

  // v[i] += x(0-origin)
  void add(int i, long long x) {
    assert(i < this->n);

    while (i < this->n) {
      this->v.at(i) += x;
      i |= i + 1;
    }
  }
};

using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  LL N, Q;
  cin >> N >> Q;

  auto A = make_v<int>(N);
  FOR(i, 0, N) { cin >> A[i]; }

  vector<int> pre_idx(N + 1, -1);
  auto next = make_v<int>(N);
  fill_v(next, -1);
  FOR(i, 0, N) {
    int l = pre_idx[A[i]];
    if (l != -1) {
      next[l] = i;
    }
    pre_idx[A[i]] = i;
  }

  auto query = make_v<pair<int, int>>(N, 0);
  FOR(i, 0, Q) {
    int L, R;
    cin >> L >> R;
    L--;
    query[L].emplace_back(make_pair(R, i));
  }

  auto ans = make_v<int>(Q);
  FenwickTree<LL> ft(500100);
  for (int l = N - 1; l >= 0; --l) {
    if (next[l] != -1) {
      ft.add(next[l], 1);
    }

    for (auto p : query[l]) {
      int r = p.first, i = p.second;
      ans[i] = (r - l) - ft.sum(r);
    }
  }

  FOR(i, 0, Q) { print(ans[i]); }

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <array>
#include <assert.h>
#include <bitset>
#include <climits>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define LEN(x) (long long)(x.size())
#define FOR(i, a, n) for (int i = (a); i < (n); ++i)
#define FOE(i, a) for (auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_COUNT(bit) (__builtin_popcount(bit))

typedef long long LL;
template <typename T> std::vector<T> make_v(size_t a) {
  return std::vector<T>(a);
}
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return std::vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
} // C++14
template <typename T, typename V>
typename std::enable_if<std::is_class<T>::value == 0>::type fill_v(T &t,
                                                                   const V &v) {
  t = v;
}
template <typename T, typename V>
typename std::enable_if<std::is_class<T>::value != 0>::type fill_v(T &t,
                                                                   const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
template <class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
void print() { std::cout << std::endl; }
template <class Head, class... Tail> void print(Head &&head, Tail &&...tail) {
  std::cout << head;
  if (sizeof...(tail) != 0) {
    std::cout << " ";
  }
  print(std::forward<Tail>(tail)...);
}
template <class T> void print(std::vector<T> &v) {
  for (auto &a : v) {
    std::cout << a;
    if (&a != &v.back()) {
      std::cout << " ";
    }
  }
  std::cout << std::endl;
}
template <class T> void print(std::vector<std::vector<T>> &vv) {
  for (auto &v : vv) {
    print(v);
  }
}
void debug() { std::cerr << std::endl; }
template <class Head, class... Tail> void debug(Head &&head, Tail &&...tail) {
  std::cerr << head;
  if (sizeof...(tail) != 0) {
    std::cerr << " ";
  }
  print(std::forward<Tail>(tail)...);
}
template <class T> void debug(std::vector<T> &v) {
  for (auto &a : v) {
    std::cerr << a;
    if (&a != &v.back()) {
      std::cerr << " ";
    }
  }
  std::cerr << std::endl;
}
template <class T> void debug(std::vector<std::vector<T>> &vv) {
  for (auto &v : vv) {
    print(v);
  }
}
inline bool inside(long long y, long long x, long long H, long long W) {
  return 0 <= y and y < H and 0 <= x and x < W;
}
template <class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
template <class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) {
  return abs(x1 - x2) + abs(y1 - y2);
}
template <typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }
bool is_bit_on(const unsigned long long bit, const unsigned int i) {
  return (bit >> i) & 1u;
}
unsigned long long bit_set(const unsigned long long bit, const unsigned int i,
                           const unsigned int b) {
  assert(b == 0 or b == 1);
  if (b == 0) {
    return bit & ~(1ull << i);
  } else {
    return bit | (1ull << i);
  }
}

// 初項s交差d長さnの数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
  return n * (2 * s + (n - 1) * d) / 2;
}

// xが2の階乗かどうか判定
bool is_power_of_two(long long x) { return !(x & (x - 1)); }

long long gcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}

long long gcd(std::vector<long long> &v) {
  long long ans = v[0];
  for (int i = 1; i < (int)v.size(); ++i) {
    ans = gcd(ans, v[i]);
  }
  return ans;
}

long long lcm(long long a, long long b) {
  long long g = gcd(a, b);
  return a / g * b;
}

const int INF = 1u << 30u; // 1,073,741,824
const long long LINF = 1ull << 60u;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};
const std::vector<int> dy4 = {0, 1, 0, -1}, dx4 = {1, 0, -1, 0};
const std::vector<int> dy8 = {0, -1, 0, 1, 1, -1, -1, 1},
                       dx8 = {1, 0, -1, 0, 1, 1, -1, -1};

class Mo {
public:
  std::vector<int> left, right; // query
  std::vector<int> order;
  std::vector<bool> v;
  int width;
  int nl, nr, ptr;

  Mo(int n) : width((int)sqrt(n)), nl(0), nr(0), ptr(0), v(n) {}

  // [l, r)
  void add_query(int l, int r) {
    this->left.emplace_back(l);
    this->right.emplace_back(r);
  }

  /* ソート */
  void build() {
    order.resize(left.size());
    std::iota(begin(order), end(order), 0);
    std::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];
    });
  }

  /* クエリを 1 つぶんすすめて, クエリのidを返す */
  int process() {
    if (ptr == order.size()) {
      return (-1);
    }

    const auto id = order[ptr];

    while (nl > left[id]) {
      distribute(--nl);
    }
    while (nr < right[id]) {
      distribute(nr++);
    }
    while (nl < left[id]) {
      distribute(nl++);
    }
    while (nr > right[id]) {
      distribute(--nr);
    }

    return order[ptr++];
  }

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

  void add(int idx);

  void del(int idx);
};

std::vector<int> A, cnt;
int sum;

void Mo::add(int idx) {
  if (cnt[A[idx]]++ == 0) {
    ++sum;
  }
}

void Mo::del(int idx) {
  if (--cnt[A[idx]] == 0) {
    --sum;
  }
}

using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  LL N, Q;
  cin >> N >> Q;

  A = make_v<int>(N);
  cnt = make_v<int>(N);
  FOR(i, 0, N) { cin >> A[i]; }

  Mo mo(N);

  FOR(i, 0, Q) {
    LL L, R;
    cin >> L >> R;
    L--;
    mo.add_query(L, R);
  }

  mo.build();

  auto ans = make_v<int>(Q);
  FOR(i, 0, Q) {
    int idx = mo.process();
    ans[idx] = sum;
  }
  FOR(i, 0, Q) { print(ans[i]); }

  return 0;
}