Problem p02594 (C++) — buggy submission, verdict: Runtime Error

#ifndef LOCAL
#pragma GCC optimize("O3")
#endif
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/detail/standard_policies.hpp>
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
using namespace std;
using namespace __gnu_pbds;
#define sim template <class c
#define int long long
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \\
  sim > typename enable_if<sizeof dud<c>(0) x 1, debug &>::type operator<<(    \\
            c i) {
sim > struct rge {
  c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << '\\n'; }
  eni(!=) cerr << boolalpha << i;
  ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
  sim dor(const c &) { ris; }
#endif
}
;
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
#define fastio                                                                 \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);
typedef tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,
             tree_order_statistics_node_update>
    ordered_set;
typedef long long ll;
const ll MOD = 1e9 + 7;
const ll N = 2e5 + 10;
const ll INF = 1e18 + 10;
signed main() {
  fastio int n;
  cin >> n;
  if (n >= 30)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}

Error: WA

Fixed submission:

#ifndef LOCAL
#pragma GCC optimize("O3")
#endif
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/detail/standard_policies.hpp>
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
using namespace std;
using namespace __gnu_pbds;
#define sim template <class c
#define int long long
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \\
  sim > typename enable_if<sizeof dud<c>(0) x 1, debug &>::type operator<<(    \\
            c i) {
sim > struct rge {
  c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << '\\n'; }
  eni(!=) cerr << boolalpha << i;
  ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
  sim dor(const c &) { ris; }
#endif
}
;
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
#define fastio                                                                 \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);
typedef tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,
             tree_order_statistics_node_update>
    ordered_set;
typedef long long ll;
const ll MOD = 1e9 + 7;
const ll N = 5e5 + 10;
const ll INF = 1e18 + 10;
int block = 0;
struct Q {
  int L, R, idx;
  // bool operator<(const Q &c){
  //     if ( L / block != c.L / block ){
  //         return L / block < c.L / block ;
  //     }
  //     return R < c.R ;
  // }
};
// bool compare(Q &x , Q &y){
//     if ( x.L / block != y.L / block ){
//         return x.L / block < y.L / block ;
//     }
//     return x.R < y.R ;
// }
bool compare(Q &x, Q &y) {
  return make_pair(x.L / block, x.R) < make_pair(y.L / block, y.R);
}
signed main() {
  fastio int n, t;
  cin >> n >> t;
  block = (int)sqrt(n + 0.0) + 1;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  vector<Q> q(t);
  for (int i = 0; i < t; i++) {
    cin >> q[i].L >> q[i].R;
    q[i].L--, q[i].R--;
    q[i].idx = i;
  }
  sort(q.begin(), q.end(), compare);
  for (Q &c : q) {
    debug() << imie(c.L) imie(c.R);
  }
  // map<int,int> mp ;
  // vector<int> mp(N) ;
  int mp[N] = {0};
  mp[v[0]]++;
  int answer = 1;
  int curL = 0, curR = 0;
  vector<int> ans(t);
  for (int i = 0; i < t; i++) {
    int L = q[i].L, R = q[i].R, idx = q[i].idx;
    while (curL > L) {
      curL--;
      int &x = v[curL];
      mp[x]++;
      if (mp[x] == 1)
        answer++;
    }
    while (curR < R) {
      curR++;
      int &x = v[curR];
      mp[x]++;
      if (mp[x] == 1)
        answer++;
    }
    while (curL < L) {
      int &x = v[curL];
      if (mp[x] > 0) {
        mp[x]--;
        if (mp[x] == 0)
          answer--;
      }
      curL++;
    }
    while (curR > R) {
      int &x = v[curR];
      if (mp[x] > 0) {
        mp[x]--;
        if (mp[x] == 0)
          answer--;
      }
      curR--;
    }
    // debug() << imie(mp) ;
    // debug() << imie(L + 1) imie(R + 1) imie(get()) ;
    ans[idx] = answer;
  }
  for (int &c : ans) {
    cout << c << endl;
  }
  return 0;
}