Problem p02598 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)

template <class T> inline void chmin(T &a, T b) {
  if (a > b)
    a = b;
}
template <class T> inline void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

// vector出力
template <class T> ostream &operator<<(ostream &o, const vector<T> &v) {
  o << "{";
  for (int i = 0; i < (int)v.size(); i++)
    o << (i > 0 ? ", " : "") << v[i];
  o << "}" << endl;
  return o;
}

// 逆元　a/b の modをとるとき -> a*modinv(b)%mod
long long modinv(long long a, long long m = 1e9 + 7) {
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
ll const mod = 1e9 + 7;

// combination
const int MAX = 510000;
const ll MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
long long COM(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

// べき乗
ll modpow(ll x, ll n) {
  x = x % MOD;
  if (n == 0)
    return 1; // 再帰の終了条件

  else if (n % 2 == 1) {
    return (x * modpow(x, n - 1)) % MOD; // nが奇数ならnを1ずらす
  } else
    return modpow((x * x) % MOD, n / 2) % MOD; // nが偶数ならnが半分になる
}

int main() {
  int N;
  ll K;
  cin >> N >> K;
  vector<ll> A(N);
  rep(i, N) { cin >> A[i]; }
  sort(A.begin(), A.end());
  ll ok = 1e9 + 1, ng = 0, now;
  while (ok - ng > 1) {
    ll cnt = 0;
    now = (ok + ng) / 2;
    for (ll i = 1; i < 1e9; i++) {
      if (upper_bound(A.begin(), A.end(), now * i) == A.end())
        break;
      cnt += i * (upper_bound(A.begin(), A.end(), now * (i + 1)) -
                  upper_bound(A.begin(), A.end(), now * i));
    }
    if (cnt > K) {
      ng = now;
      // cout << now << ' ' << cnt << ';' << "ng" << endl;
    } else {
      ok = now;
      // cout << now << ' ' << cnt << ';' << "ok" << endl;
    }
  }
  cout << ok << endl;
}


Fixed submission:
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)

template <class T> inline void chmin(T &a, T b) {
  if (a > b)
    a = b;
}
template <class T> inline void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

// vector出力
template <class T> ostream &operator<<(ostream &o, const vector<T> &v) {
  o << "{";
  for (int i = 0; i < (int)v.size(); i++)
    o << (i > 0 ? ", " : "") << v[i];
  o << "}" << endl;
  return o;
}

// 逆元　a/b の modをとるとき -> a*modinv(b)%mod
long long modinv(long long a, long long m = 1e9 + 7) {
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}
ll const mod = 1e9 + 7;

// combination
const int MAX = 510000;
const ll MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
long long COM(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

// べき乗
ll modpow(ll x, ll n) {
  x = x % MOD;
  if (n == 0)
    return 1; // 再帰の終了条件

  else if (n % 2 == 1) {
    return (x * modpow(x, n - 1)) % MOD; // nが奇数ならnを1ずらす
  } else
    return modpow((x * x) % MOD, n / 2) % MOD; // nが偶数ならnが半分になる
}

int main() {
  int N;
  ll K;
  cin >> N >> K;
  vector<ll> A(N);
  rep(i, N) { cin >> A[i]; }
  sort(A.begin(), A.end());
  ll ok = 1e9 + 1, ng = 0, now;
  while (ok - ng > 1) {
    ll cnt = 0;
    now = (ok + ng) / 2;
    // for (ll i=1;i<1e9;i++) {
    //   if (upper_bound(A.begin(),A.end(),now*i)==A.end()) break;
    //   cnt += i*(upper_bound(A.begin(),A.end(),now*(i+1)) -
    //   upper_bound(A.begin(),A.end(),now*i));

    // }
    rep(i, N) cnt += (A[i] - 1) / now;
    if (cnt > K) {
      ng = now;
      // cout << now << ' ' << cnt << ';' << "ng" << endl;
    } else {
      ok = now;
      // cout << now << ' ' << cnt << ';' << "ok" << endl;
    }
  }
  cout << ok << endl;
}