Problem p02598 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a) for (int i = 0; i < (a); i++)
typedef long long ll;

#ifdef _DEBUG
inline void dump() { cerr << endl; }
template <typename Head> void dump(Head &&head) {
  cerr << head;
  dump();
}
template <typename Head, typename... Tail>
void dump(Head &&head, Tail &&...tail) {
  cerr << head << ", ";
  dump(forward<Tail>(tail)...);
}
#define debug(...)                                                             \
  do {                                                                         \
    cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = ";                        \
    dump(__VA_ARGS__);                                                         \
  } while (false)
#else
#define dump(...)
#define debug(...)
#endif

template <typename T> struct edge {
  int src, to;
  T cost;
  edge(int to, T cost) : src(-1), to(to), cost(cost) {}
  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}
  edge &operator=(const int &x) {
    to = x;
    return *this;
  }
  operator int() const { return to; }
};
template <typename T> using Edges = vector<edge<T>>;
template <typename T> using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;
template <typename T> using Matrix = vector<vector<T>>;

/////////////////////////////////////////////////////////////////////

const ll inf = 1LL << 60;

int main() {
  ll n, k;
  cin >> n >> k;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];

  ll l = 0;
  ll r = 1000000001;

  while (l < r) {
    ll m = (l + r) / 2;
    ll t = 0;
    rep(i, n) { t += (a[i] - 1) / m; }
    if (t <= k)
      r = m;
    else
      l = m + 1;
  }
  cout << l << endl;

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a) for (int i = 0; i < (a); i++)
typedef long long ll;

#ifdef _DEBUG
inline void dump() { cerr << endl; }
template <typename Head> void dump(Head &&head) {
  cerr << head;
  dump();
}
template <typename Head, typename... Tail>
void dump(Head &&head, Tail &&...tail) {
  cerr << head << ", ";
  dump(forward<Tail>(tail)...);
}
#define debug(...)                                                             \
  do {                                                                         \
    cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = ";                        \
    dump(__VA_ARGS__);                                                         \
  } while (false)
#else
#define dump(...)
#define debug(...)
#endif

template <typename T> struct edge {
  int src, to;
  T cost;
  edge(int to, T cost) : src(-1), to(to), cost(cost) {}
  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}
  edge &operator=(const int &x) {
    to = x;
    return *this;
  }
  operator int() const { return to; }
};
template <typename T> using Edges = vector<edge<T>>;
template <typename T> using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;
template <typename T> using Matrix = vector<vector<T>>;

/////////////////////////////////////////////////////////////////////

const ll inf = 1LL << 60;

int main() {
  ll n, k;
  cin >> n >> k;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];

  ll l = 1;
  ll r = 1000000001;

  while (l < r) {
    ll m = (l + r) / 2;
    ll t = 0;
    rep(i, n) { t += (a[i] - 1) / m; }
    if (t <= k)
      r = m;
    else
      l = m + 1;
  }
  cout << l << endl;

  return 0;
}