Problem p02599 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define ll long long
#define all(v) v.begin(), v.end()
#define PB push_back
#define PI 3.1415926535897932384626433832795
#define what(x) cout << #x << " is " << x << endl;
using namespace std;

template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

ll powmod(ll a, ll b, ll mod) {
  ll res = 1;
  a %= mod;
  // assert(b>=0);
  for (; b; b >>= 1) {
    if (b & 1)
      res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
const int mxn = 1e5 + 1;
int fin[mxn];
int lst[mxn];
int n, q;
vector<int> c;
void update(int ind, int val) {
  while (ind <= n) {
    fin[ind] += val;
    ind += ind & -ind;
  }
}
int query(int ind) {
  int ret = 0;
  while (ind > 0) {
    ret += fin[ind];
    ind -= ind & -ind;
  }
  return ret;
}

struct Query {
  int l, r, ind;
  bool operator()(Query a, Query b) { return a.r < b.r; }
};

void solve() {
  memset(lst, -1, sizeof(lst));
  cin >> n >> q;
  int ans[q];
  c.resize(n);
  for (int i = 0; i < n; i++) {
    cin >> c[i];
  }
  Query qry[q];
  for (int i = 0; i < q; i++) {
    qry[i].ind = i;
    cin >> qry[i].l >> qry[i].r;
    qry[i].l--, qry[i].r--;
  }
  sort(qry, qry + q, Query());
  for (int j = 0, i = 0; i < n; i++) {
    if (lst[c[i]] != -1) {
      update(lst[c[i]] + 1, -1);
    }
    lst[c[i]] = i;
    update(i + 1, 1);
    while (j < q && qry[j].r == i) {
      ans[qry[j].ind] = query(qry[j].r + 1) - query(qry[j].l);
      j++;
    }
  }
  for (int i = 0; i < q; i++) {
    cout << ans[i] << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tc = 1;
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
#endif
  // cin>>tc;
  while (tc--)
    solve();
}


Fixed submission:
#include <bits/stdc++.h>
#define ll long long
#define all(v) v.begin(), v.end()
#define PB push_back
#define PI 3.1415926535897932384626433832795
#define what(x) cout << #x << " is " << x << endl;
using namespace std;

template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

ll powmod(ll a, ll b, ll mod) {
  ll res = 1;
  a %= mod;
  // assert(b>=0);
  for (; b; b >>= 1) {
    if (b & 1)
      res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
const int mxn = 5e5 + 1;
int fin[mxn];
int lst[mxn];
int n, q;
vector<int> c;
void update(int ind, int val) {
  while (ind <= n) {
    fin[ind] += val;
    ind += ind & -ind;
  }
}
int query(int ind) {
  int ret = 0;
  while (ind > 0) {
    ret += fin[ind];
    ind -= ind & -ind;
  }
  return ret;
}

struct Query {
  int l, r, ind;
  bool operator()(Query a, Query b) { return a.r < b.r; }
};

void solve() {
  memset(lst, -1, sizeof(lst));
  cin >> n >> q;
  int ans[q];
  c.resize(n);
  for (int i = 0; i < n; i++) {
    cin >> c[i];
  }
  Query qry[q];
  for (int i = 0; i < q; i++) {
    qry[i].ind = i;
    cin >> qry[i].l >> qry[i].r;
    qry[i].l--, qry[i].r--;
  }
  sort(qry, qry + q, Query());
  for (int j = 0, i = 0; i < n; i++) {
    if (lst[c[i]] != -1) {
      update(lst[c[i]] + 1, -1);
    }
    lst[c[i]] = i;
    update(i + 1, 1);
    while (j < q && qry[j].r == i) {
      ans[qry[j].ind] = query(qry[j].r + 1) - query(qry[j].l);
      j++;
    }
  }
  for (int i = 0; i < q; i++) {
    cout << ans[i] << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tc = 1;
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
#endif
  // cin>>tc;
  while (tc--)
    solve();
}