Problem p02599 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define ff first
#define ss second
#define ll int64_t
#define ld long double
#define nl cout << "\n"
#define dbg(x) cerr << #x << " = " << x << "\n"
#define dbg2(x, y) cerr << #x << " = " << x << "   " << #y << " = " << y << "\n"
#define all(v) v.begin(), v.end()
#define mset(a, v) memset((a), (v), sizeof(a))
#define forn(i, a, b) for (int64_t i = int64_t(a); i < int64_t(b); ++i)
#define forb(i, a, b) for (int64_t i = int64_t(a); i >= int64_t(b); --i)
#define fastio()                                                               \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define ordered_set                                                            \
  tree<int, null_type, less<int>, rb_tree_tag,                                 \
       tree_order_statistics_node_update>

#define mod 1000000007
#define mod2 998244353
#define inf 1000000000000007
#define pi 3.14159265358979323846

template <typename T, typename U> static inline void amin(T &x, U y) {
  if (y < x)
    x = y;
}
template <typename T, typename U> static inline void amax(T &x, U y) {
  if (x < y)
    x = y;
}
template <class L, class R> ostream &operator<<(ostream &out, pair<L, R> &p) {
  return out << "(" << p.ff << ", " << p.ss << ")";
}
template <class T> ostream &operator<<(ostream &out, vector<T> &v) {
  out << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      out << ", ";
    out << *it;
  }
  return out << "]";
}
template <class T> ostream &operator<<(ostream &out, deque<T> &v) {
  out << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      out << ", ";
    out << *it;
  }
  return out << "]";
}
template <class T> ostream &operator<<(ostream &out, set<T> &s) {
  out << "{";
  for (auto it = s.begin(); it != s.end(); ++it) {
    if (it != s.begin())
      out << ", ";
    out << *it;
  }
  return out << "}";
}
template <class L, class R> ostream &operator<<(ostream &out, map<L, R> &m) {
  out << "{";
  for (auto it = m.begin(); it != m.end(); ++it) {
    if (it != m.begin())
      out << ", ";
    out << *it;
  }
  return out << "}";
}

ll count_digits(ll n) {
  ll dig = floor(log10(n) + 1);
  return dig;
}
ll mpow(ll x, ll y, ll p) {
  ll r = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1)
      r = (r * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return r;
}
string dec_bin_32(ll n) {
  string s;
  for (ll i = 31; i >= 0; i--) {
    ll k = n >> i;
    s += (k & 1) ? '1' : '0';
  }
  return s;
}
string dec_bin_64(ll n) {
  string s;
  for (ll i = 63; i >= 0; i--) {
    ll k = n >> i;
    s += (k & 1) ? '1' : '0';
  }
  return s;
}
ll mod_inv(ll a, ll m) {
  ll m0 = m, y = 0, x = 1;
  if (m == 1)
    return 0;
  while (a > 1) {
    ll q = a / m, t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0)
    x += m0;
  return x;
}
/* const ll MAXN=10000007;ll spf[MAXN+5];vector<ll> prime; */
/* void sieve(ll n)        {forn(i,2,MAXN+1)spf[i]=i;for(ll
 * i=2;i*i<=n;i++)if(spf[i]==i)for(ll
 * j=i*i;j<=n;j+=i)if(spf[j]==j)spf[j]=i;forn(i,2,MAXN+1)if(spf[i]==i)prime.push_back(i);}
 */

//-------------------------------L_I_Erq34-------------------------------

vector<vector<ll>> segtree;
vector<ll> b;

void construct(ll st, ll end, ll i) {
  if (st == end) {
    segtree[i].push_back(b[st]);
    return;
  }
  ll mid = (st + end) >> 1;
  construct(st, mid, 2 * i + 1);
  construct(mid + 1, end, 2 * i + 2);
  segtree[i].resize(segtree[2 * i + 1].size() + segtree[2 * i + 2].size());
  merge(all(segtree[2 * i + 1]), all(segtree[2 * i + 2]), segtree[i].begin());
}

ll query(ll l, ll h, ll st, ll end, ll i, ll k) {
  if (l <= st and h >= end)
    return upper_bound(all(segtree[i]), k) - segtree[i].begin();
  if (l > end or h < st)
    return 0;
  ll mid = (st + end) >> 1;
  return query(l, h, st, mid, 2 * i + 1, k) +
         query(l, h, mid + 1, end, 2 * i + 2, k);
}

int main() {
  fastio();
  ll z, n, m, t, k, i, j, l, d, h, r;
  ll q;
  cin >> n >> q;
  vector<ll> a(n), ind(n + 1, inf);
  b.resize(n);
  for (ll &i : a)
    cin >> i;
  forb(i, n - 1, 0) {
    b[i] = ind[a[i]];
    ind[a[i]] = i;
  }
  dbg(b);
  segtree.resize(n << 2);
  construct(0, n - 1, 0);
  while (q--) {
    cin >> l >> r;
    l--, r--;
    k = r - l + 1 - query(l, r, 0, n - 1, 0, r);
    cout << k << "\n";
  }
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define ff first
#define ss second
#define ll int64_t
#define ld long double
#define nl cout << "\n"
#define dbg(x) cerr << #x << " = " << x << "\n"
#define dbg2(x, y) cerr << #x << " = " << x << "   " << #y << " = " << y << "\n"
#define all(v) v.begin(), v.end()
#define mset(a, v) memset((a), (v), sizeof(a))
#define forn(i, a, b) for (int64_t i = int64_t(a); i < int64_t(b); ++i)
#define forb(i, a, b) for (int64_t i = int64_t(a); i >= int64_t(b); --i)
#define fastio()                                                               \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define ordered_set                                                            \
  tree<int, null_type, less<int>, rb_tree_tag,                                 \
       tree_order_statistics_node_update>

#define mod 1000000007
#define mod2 998244353
#define inf 1000000000000007
#define pi 3.14159265358979323846

template <typename T, typename U> static inline void amin(T &x, U y) {
  if (y < x)
    x = y;
}
template <typename T, typename U> static inline void amax(T &x, U y) {
  if (x < y)
    x = y;
}
template <class L, class R> ostream &operator<<(ostream &out, pair<L, R> &p) {
  return out << "(" << p.ff << ", " << p.ss << ")";
}
template <class T> ostream &operator<<(ostream &out, vector<T> &v) {
  out << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      out << ", ";
    out << *it;
  }
  return out << "]";
}
template <class T> ostream &operator<<(ostream &out, deque<T> &v) {
  out << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin())
      out << ", ";
    out << *it;
  }
  return out << "]";
}
template <class T> ostream &operator<<(ostream &out, set<T> &s) {
  out << "{";
  for (auto it = s.begin(); it != s.end(); ++it) {
    if (it != s.begin())
      out << ", ";
    out << *it;
  }
  return out << "}";
}
template <class L, class R> ostream &operator<<(ostream &out, map<L, R> &m) {
  out << "{";
  for (auto it = m.begin(); it != m.end(); ++it) {
    if (it != m.begin())
      out << ", ";
    out << *it;
  }
  return out << "}";
}

ll count_digits(ll n) {
  ll dig = floor(log10(n) + 1);
  return dig;
}
ll mpow(ll x, ll y, ll p) {
  ll r = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1)
      r = (r * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return r;
}
string dec_bin_32(ll n) {
  string s;
  for (ll i = 31; i >= 0; i--) {
    ll k = n >> i;
    s += (k & 1) ? '1' : '0';
  }
  return s;
}
string dec_bin_64(ll n) {
  string s;
  for (ll i = 63; i >= 0; i--) {
    ll k = n >> i;
    s += (k & 1) ? '1' : '0';
  }
  return s;
}
ll mod_inv(ll a, ll m) {
  ll m0 = m, y = 0, x = 1;
  if (m == 1)
    return 0;
  while (a > 1) {
    ll q = a / m, t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0)
    x += m0;
  return x;
}
/* const ll MAXN=10000007;ll spf[MAXN+5];vector<ll> prime; */
/* void sieve(ll n)        {forn(i,2,MAXN+1)spf[i]=i;for(ll
 * i=2;i*i<=n;i++)if(spf[i]==i)for(ll
 * j=i*i;j<=n;j+=i)if(spf[j]==j)spf[j]=i;forn(i,2,MAXN+1)if(spf[i]==i)prime.push_back(i);}
 */

//-------------------------------L_I_Erq34-------------------------------

vector<vector<ll>> segtree;
vector<ll> b;

void construct(ll st, ll end, ll i) {
  if (st == end) {
    segtree[i].push_back(b[st]);
    return;
  }
  ll mid = (st + end) >> 1;
  construct(st, mid, 2 * i + 1);
  construct(mid + 1, end, 2 * i + 2);
  segtree[i].resize(segtree[2 * i + 1].size() + segtree[2 * i + 2].size());
  merge(all(segtree[2 * i + 1]), all(segtree[2 * i + 2]), segtree[i].begin());
}

ll query(ll l, ll h, ll st, ll end, ll i, ll k) {
  if (l <= st and h >= end)
    return upper_bound(all(segtree[i]), k) - segtree[i].begin();
  if (l > end or h < st)
    return 0;
  ll mid = (st + end) >> 1;
  return query(l, h, st, mid, 2 * i + 1, k) +
         query(l, h, mid + 1, end, 2 * i + 2, k);
}

int main() {
  fastio();
  ll z, n, m, t, k, i, j, l, d, h, r;
  ll q;
  cin >> n >> q;
  vector<ll> a(n), ind(n + 1, inf);
  b.resize(n);
  for (ll &i : a)
    cin >> i;
  forb(i, n - 1, 0) {
    b[i] = ind[a[i]];
    ind[a[i]] = i;
  }
  segtree.resize(n << 2);
  construct(0, n - 1, 0);
  while (q--) {
    cin >> l >> r;
    l--, r--;
    k = r - l + 1 - query(l, r, 0, n - 1, 0, r);
    cout << k << "\n";
  }
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}