Problem p02358 (C++) — buggy submission, verdict: Runtime Error

#include "bits/stdc++.h"
using namespace std;
using LL = long long;
using ULL = unsigned long long;
const double PI = acos(-1);
template <class T> constexpr T INF() { return ::std::numeric_limits<T>::max(); }
template <class T> constexpr T HINF() { return INF<T>() / 2; }
template <typename T_char> T_char TL(T_char cX) { return tolower(cX); };
template <typename T_char> T_char TU(T_char cX) { return toupper(cX); };
typedef pair<LL, LL> pii;
const int vy[] = {-1, -1, -1, 0, 1, 1, 1, 0},
          vx[] = {-1, 0, 1, 1, 1, 0, -1, -1};
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, -1, 0, 1};
const char dir[4] = {'u', 'l', 'd', 'r'};
int popcnt(unsigned long long n) {
  int cnt = 0;
  for (int i = 0; i < 64; i++)
    if ((n >> i) & 1)
      cnt++;
  return cnt;
}
int d_sum(LL n) {
  int ret = 0;
  while (n > 0) {
    ret += n % 10;
    n /= 10;
  }
  return ret;
}
int d_cnt(LL n) {
  int ret = 0;
  while (n > 0) {
    ret++;
    n /= 10;
  }
  return ret;
}
LL gcd(LL a, LL b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
};
LL lcm(LL a, LL b) {
  LL g = gcd(a, b);
  return a / g * b;
};
#define ALL(qpqpq) (qpqpq).begin(), (qpqpq).end()
#define UNIQUE(wpwpw)                                                          \\
  sort(ALL((wpwpw)));                                                          \\
  (wpwpw).erase(unique(ALL((wpwpw))), (wpwpw).end())
#define LOWER(epepe) transform(ALL((epepe)), (epepe).begin(), TL<char>)
#define UPPER(rprpr) transform(ALL((rprpr)), (rprpr).begin(), TU<char>)
#define FOR(i, tptpt, ypypy) for (LL i = (tptpt); i < (ypypy); i++)
#define REP(i, upupu) FOR(i, 0, upupu)
#define INIT                                                                   \\
  std::ios::sync_with_stdio(false);                                            \\
  std::cin.tie(0)
#pragma warning(disable : 4996)

int n;
LL x1[2020], x2[2020], y334[2020], y2[2020];
int iscover[4040][4040];
int main() {
  cin >> n;
  vector<LL> x, y;
  REP(i, n) {
    cin >> x1[i] >> y334[i] >> x2[i] >> y2[i];
    x.emplace_back(x1[i]);
    x.emplace_back(x2[i]);
    y.emplace_back(y334[i]);
    y.emplace_back(y2[i]);
  }
  UNIQUE(x);
  UNIQUE(y);
  REP(i, n) {
    int xx1 = lower_bound(ALL(x), x1[i]) - x.begin();
    int xx2 = lower_bound(ALL(x), x2[i]) - x.begin();
    int yy1 = lower_bound(ALL(y), y334[i]) - y.begin();
    int yy2 = lower_bound(ALL(y), y2[i]) - y.begin();
    iscover[yy1][xx1]++;
    iscover[yy2][xx1]--;
    iscover[yy1][xx2]--;
    iscover[yy2][xx2]++;
  }
  REP(i, 4040) {
    REP(j, 4040) {
      if (j)
        iscover[i][j] += iscover[i][j - 1];
    }
  }
  REP(j, 4040) {
    REP(i, 4040) {
      if (i)
        iscover[i][j] += iscover[i - 1][j];
    }
  }
  LL ans = 0;
  REP(i, 4040) REP(j, 4040) {
    if (iscover[i][j] > 0) {
      ans += (x[j + 1] - x[j]) * (y[i + 1] - y[i]);
    }
  }
  cout << ans << endl;
  // system("pause");
}


Error: 0

Fixed submission:

#include "bits/stdc++.h"
using namespace std;
using LL = long long;
using ULL = unsigned long long;
const double PI = acos(-1);
template <class T> constexpr T INF() { return ::std::numeric_limits<T>::max(); }
template <class T> constexpr T HINF() { return INF<T>() / 2; }
template <typename T_char> T_char TL(T_char cX) { return tolower(cX); };
template <typename T_char> T_char TU(T_char cX) { return toupper(cX); };
typedef pair<LL, LL> pii;
const int vy[] = {-1, -1, -1, 0, 1, 1, 1, 0},
          vx[] = {-1, 0, 1, 1, 1, 0, -1, -1};
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, -1, 0, 1};
const char dir[4] = {'u', 'l', 'd', 'r'};
int popcnt(unsigned long long n) {
  int cnt = 0;
  for (int i = 0; i < 64; i++)
    if ((n >> i) & 1)
      cnt++;
  return cnt;
}
int d_sum(LL n) {
  int ret = 0;
  while (n > 0) {
    ret += n % 10;
    n /= 10;
  }
  return ret;
}
int d_cnt(LL n) {
  int ret = 0;
  while (n > 0) {
    ret++;
    n /= 10;
  }
  return ret;
}
LL gcd(LL a, LL b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
};
LL lcm(LL a, LL b) {
  LL g = gcd(a, b);
  return a / g * b;
};
#define ALL(qpqpq) (qpqpq).begin(), (qpqpq).end()
#define UNIQUE(wpwpw)                                                          \\
  sort(ALL((wpwpw)));                                                          \\
  (wpwpw).erase(unique(ALL((wpwpw))), (wpwpw).end())
#define LOWER(epepe) transform(ALL((epepe)), (epepe).begin(), TL<char>)
#define UPPER(rprpr) transform(ALL((rprpr)), (rprpr).begin(), TU<char>)
#define FOR(i, tptpt, ypypy) for (LL i = (tptpt); i < (ypypy); i++)
#define REP(i, upupu) FOR(i, 0, upupu)
#define INIT                                                                   \\
  std::ios::sync_with_stdio(false);                                            \\
  std::cin.tie(0)
#pragma warning(disable : 4996)

int n;
LL x1[2020], x2[2020], y334[2020], y2[2020];
int iscover[2020][2020];
int main() {
  cin >> n;
  vector<LL> x, y;
  REP(i, n) {
    cin >> x1[i] >> y334[i] >> x2[i] >> y2[i];
    x.emplace_back(x1[i]);
    x.emplace_back(x2[i]);
    y.emplace_back(y334[i]);
    y.emplace_back(y2[i]);
  }
  UNIQUE(x);
  UNIQUE(y);
  REP(i, n) {
    int xx1 = lower_bound(ALL(x), x1[i]) - x.begin();
    int xx2 = lower_bound(ALL(x), x2[i]) - x.begin();
    int yy1 = lower_bound(ALL(y), y334[i]) - y.begin();
    int yy2 = lower_bound(ALL(y), y2[i]) - y.begin();
    iscover[yy1][xx1]++;
    iscover[yy2][xx1]--;
    iscover[yy1][xx2]--;
    iscover[yy2][xx2]++;
  }
  REP(i, 2020) {
    REP(j, 2020) {
      if (j)
        iscover[i][j] += iscover[i][j - 1];
    }
  }
  REP(j, 2020) {
    REP(i, 2020) {
      if (i)
        iscover[i][j] += iscover[i - 1][j];
    }
  }
  LL ans = 0;
  REP(i, 2020) REP(j, 2020) {
    if (iscover[i][j] > 0) {
      ans += (x[j + 1] - x[j]) * (y[i + 1] - y[i]);
    }
  }
  cout << ans << endl;
}