Problem p03221 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define drrep(i, n) for (int i = n; i > 0; --i)
#define srep(i, s, t) for (int i = s; i < t; ++i)

#define rng(a) a.begin(), a.end()
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

#define chmax(x, y) (x = max(x, y))
#define chmin(x, y) (x = min(x, y))

using pi = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
using ll = long long;
using ld = long double;

template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  rep(i, (int)v.size()) {
    if (i)
      os << ",";
    os << v[i];
  }
  os << "}";
  return os;
}

template <typename T, size_t S> void printArray(const T (&array)[S]) {
  for (auto val : array)
    std::cout << val << ", ";
  std::cout << "\n";
}

const int MOD = 1'000'000'000 + 7;
const int INF = 1'000'000'000 + 5;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(16);

  int n, m;
  std::cin >> n >> m;
  vi p(n), y(m);
  vvi vvp(n);
  rep(i, m) {
    std::cin >> p[i] >> y[i];
    p[i]--;
    vvp[p[i]].pb(y[i]);
  }
  rep(i, n) { sort(rng(vvp[i])); }
  rep(i, m) {
    auto it = lower_bound(rng(vvp[p[i]]), y[i]) - vvp[p[i]].begin();
    printf("%06d%06d\n", p[i] + 1, (int)it + 1);
  }
}


Fixed submission:
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define drrep(i, n) for (int i = n; i > 0; --i)
#define srep(i, s, t) for (int i = s; i < t; ++i)

#define rng(a) a.begin(), a.end()
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

#define chmax(x, y) (x = max(x, y))
#define chmin(x, y) (x = min(x, y))

using pi = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;
using ll = long long;
using ld = long double;

template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  rep(i, (int)v.size()) {
    if (i)
      os << ",";
    os << v[i];
  }
  os << "}";
  return os;
}

template <typename T, size_t S> void printArray(const T (&array)[S]) {
  for (auto val : array)
    std::cout << val << ", ";
  std::cout << "\n";
}

const int MOD = 1'000'000'000 + 7;
const int INF = 1'000'000'000 + 5;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(16);

  int n, m;
  std::cin >> n >> m;
  vi p(m), y(m);
  vvi vvp(n);
  rep(i, m) {
    std::cin >> p[i] >> y[i];
    p[i]--;
    vvp[p[i]].pb(y[i]);
  }
  rep(i, n) { sort(rng(vvp[i])); }
  rep(i, m) {
    auto it = lower_bound(rng(vvp[p[i]]), y[i]) - vvp[p[i]].begin();
    printf("%06d%06d\n", p[i] + 1, (int)it + 1);
  }
}