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

#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &o) {
  out << "(" << o.first << "," << o.second << ")";
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &V) {
  for (int i = 0; i < V.size(); i++) {
    out << V[i];
    if (i != V.size() - 1)
      out << " ";
  }
  return out;
}
template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &Mat) {
  for (int i = 0; i < Mat.size(); i++) {
    if (i != 0)
      out << endl;
    out << Mat[i];
  }
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const map<S, T> &mp) {
  out << "{ ";
  for (auto it = mp.begin(); it != mp.end(); it++) {
    out << it->first << ":" << it->second;
    if (mp.size() - 1 != distance(mp.begin(), it))
      out << ", ";
  }
  out << " }";
  return out;
}
template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */
const int MAX_N = 500005;
int ans[MAX_N];
int cnt[MAX_N];
struct Mo {

  int BlockSZ;
  int Q;
  int L[MAX_N];
  int R[MAX_N];
  int order[MAX_N];

  Mo() : Q(0), BlockSZ((int)sqrt(MAX_N)) {}

  // [l,r)  : 0-index
  void add(int l, int r) {
    L[Q] = l;
    R[Q] = r;
    order[Q] = Q;
    Q++;
  }

  void run() {
    // assert(left.size() == order.size());
    sort(order, order + Q, [&](int l, int r) {
      int lblock = L[l] / BlockSZ, rblock = L[r] / BlockSZ;
      if (lblock != rblock)
        return L[l] < L[r];
      return (lblock & 1) ? R[l] < R[r] : R[l] > R[r];
    });
    int nl = 0, nr = 0;
    for (int q = 0; q < Q; q++) {
      int idx = order[q];
      while (nl > L[idx]) {
        nl--;
        add(nl);
      }
      while (nr < R[idx]) {
        add(nr);
        nr++;
      }
      while (nl < L[idx]) {
        del(nl);
        nl++;
      }
      while (nr > R[idx]) {
        nr--;
        del(nr);
      }
      rem(idx);
    }
  }

  // ======================================== //
  // Custom
  // ======================================== //
  vector<int> a;
  int sum;

  void init(vector<int> &a) {
    sum = 0;
    this->a = a;
  }

  void add(int &id) {
    if (cnt[a[id]] == 0)
      sum++;
    cnt[a[id]]++;
  }
  void del(int &id) {
    cnt[a[id]]--;
    if (cnt[a[id]] == 0)
      sum--;
  };
  void rem(int &id) { ans[id] = sum; }
};

template <class Type> Type solve(Type res = Type()) {
  int N, Q;
  cin >> N >> Q;
  vector<int> c(N);
  for (auto &in : c)
    cin >> in;
  Mo mo;
  mo.init(c);
  for (int i = 0; i < Q; i++) {
    int l, r;
    cin >> l >> r;
    l--;
    mo.add(l, r);
  }
  mo.run();
  for (int i = 0; i < Q; i++) {
    cout << ans[i] << '\\n';
  }

  return res;
}
int main(void) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout.tie(0);
  solve(0);
  // cout << fixed << setprecision(15) << solve<ll>() << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <class S, class T>
ostream &operator<<(ostream &out, const pair<S, T> &o) {
  out << "(" << o.first << "," << o.second << ")";
  return out;
}
template <class T> ostream &operator<<(ostream &out, const vector<T> &V) {
  for (int i = 0; i < V.size(); i++) {
    out << V[i];
    if (i != V.size() - 1)
      out << " ";
  }
  return out;
}
template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &Mat) {
  for (int i = 0; i < Mat.size(); i++) {
    if (i != 0)
      out << endl;
    out << Mat[i];
  }
  return out;
}
template <class S, class T>
ostream &operator<<(ostream &out, const map<S, T> &mp) {
  out << "{ ";
  for (auto it = mp.begin(); it != mp.end(); it++) {
    out << it->first << ":" << it->second;
    if (mp.size() - 1 != distance(mp.begin(), it))
      out << ", ";
  }
  out << " }";
  return out;
}
template <typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

const int MAX_N = 500005;
struct Mo {
  using add_func = function<void(int &)>;
  using del_func = function<void(int &)>;
  using rem_func = function<void(int &)>;

  int BlockSZ;
  int Q;
  int L[MAX_N];
  int R[MAX_N];
  int order[MAX_N];
  Mo() : Q(0), BlockSZ((int)sqrt(MAX_N)) {}

  // [l,r)  : 0-index
  void add(int l, int r) {
    L[Q] = l;
    R[Q] = r;
    order[Q] = Q;
    Q++;
  }

  void run(const add_func &add, const del_func &del, const rem_func &rem) {
    // assert(left.size() == order.size());
    sort(order, order + Q, [&](int l, int r) {
      int lblock = L[l] / BlockSZ, rblock = L[r] / BlockSZ;
      if (lblock != rblock)
        return L[l] < L[r];
      return (lblock & 1) ? R[l] < R[r] : R[l] > R[r];
    });
    int nl = 0, nr = 0;
    for (int q = 0; q < Q; q++) {
      int idx = order[q];
      while (nl > L[idx]) {
        nl--;
        add(nl);
      }
      while (nr < R[idx]) {
        add(nr);
        nr++;
      }
      while (nl < L[idx]) {
        del(nl);
        nl++;
      }
      while (nr > R[idx]) {
        nr--;
        del(nr);
      }
      rem(idx);
    }
  }
};

template <class Type> Type solve(Type res = Type()) {
  int N, Q;
  cin >> N >> Q;
  vector<int> c(N);
  for (auto &in : c)
    cin >> in;
  Mo mo;
  for (int i = 0; i < Q; i++) {
    int l, r;
    cin >> l >> r;
    l--;
    mo.add(l, r);
  }

  vector<int> ans(Q);
  vector<int> cnt(N + 1);
  int sum = 0;
  auto add = [&](int &id) {
    if (cnt[c[id]] == 0)
      sum++;
    cnt[c[id]]++;
  };
  auto del = [&](int &id) {
    cnt[c[id]]--;
    if (cnt[c[id]] == 0)
      sum--;
  };
  auto rem = [&](int &id) { ans[id] = sum; };

  mo.run(add, del, rem);
  for (int i = 0; i < Q; i++) {
    cout << ans[i] << '\\n';
  }

  return res;
}
int main(void) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout.tie(0);
  solve(0);
  // cout << fixed << setprecision(15) << solve<ll>() << endl;
  return 0;
}