Problem p03202 (C++)

Buggy submission (status: Time Limit Exceeded):
#define LOCAL
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
using namespace std;
#define rep(i, x) for (ll i = 0; i < (ll)(x); i++)
#define rrep(i, x) for (ll i = (ll)(x)-1; 0 <= i; i--)
#define reps(i, x) for (ll i = 1; i < (ll)(x) + 1; i++)
#define rreps(i, x) for (ll i = (ll)(x); 1 <= i; i--)
#define all(x) (x).begin(), (x).end()
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> Pll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
constexpr ll INF = numeric_limits<ll>::max() / 4;
constexpr ll n_max = 2e5 + 10;
#define int ll

template <typename A, typename B> string to_string(pair<A, B> p);
string to_string(const string &s) { return '"' + s + '"'; }
string to_string(const char c) { return to_string((string)&c); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++)
    res += static_cast<char>('0' + v[i]);
  return res;
}
template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first)
      res += ", ";
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  ll n;
  cin >> n;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];
  auto c = [&](ll x) {
    if (x == 1) {
      bool ok = true;
      rep(i, n - 1) ok &= a[i + 1] > a[i];
      return ok;
    }
    map<ll, ll> mp;
    reps(i, n - 1) {
      if (a[i] > a[i - 1])
        continue;
      mp[a[i]]++;
      auto itr = mp.find(a[i]);
      itr++;
      mp.erase(itr, mp.end());
      if (mp[a[i]] == x) {
        ll t = a[i];
        while (mp[t] >= x) {
          mp[--t]++;
          mp.erase(t + 1);
        }
      }
    }

    return mp.count(0) == 0;
  };

  ll ok = 1e9;
  ll ng = 0;

  while (abs(ok - ng) > 1) {
    ll x = (ok + ng) / 2;
    if (c(x))
      ok = x;
    else
      ng = x;
  }

  cout << ok << endl;
  return 0;
}

Fixed submission:
#define LOCAL
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
using namespace std;
#define rep(i, x) for (ll i = 0; i < (ll)(x); i++)
#define rrep(i, x) for (ll i = (ll)(x)-1; 0 <= i; i--)
#define reps(i, x) for (ll i = 1; i < (ll)(x) + 1; i++)
#define rreps(i, x) for (ll i = (ll)(x); 1 <= i; i--)
#define all(x) (x).begin(), (x).end()
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> Pll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
constexpr ll INF = numeric_limits<ll>::max() / 4;
constexpr ll n_max = 2e5 + 10;
#define int ll

template <typename A, typename B> string to_string(pair<A, B> p);
string to_string(const string &s) { return '"' + s + '"'; }
string to_string(const char c) { return to_string((string)&c); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++)
    res += static_cast<char>('0' + v[i]);
  return res;
}
template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first)
      res += ", ";
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  ll n;
  cin >> n;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];
  auto c = [&](ll x) {
    if (x == 1) {
      bool ok = true;
      rep(i, n - 1) ok &= a[i + 1] > a[i];
      return ok;
    }
    map<ll, ll> mp;
    reps(i, n - 1) {
      if (a[i] > a[i - 1])
        continue;
      mp[a[i]]++;
      auto itr = mp.find(a[i]);
      itr++;
      mp.erase(itr, mp.end());
      if (mp[a[i]] == x) {
        ll t = a[i];
        while (mp[t] >= x) {
          mp[--t]++;
          mp.erase(t + 1);
        }
      }
    }

    return mp.count(0) == 0;
  };

  ll ok = 1e6;
  ll ng = 0;

  while (abs(ok - ng) > 1) {
    ll x = (ok + ng) / 2;
    if (c(x))
      ok = x;
    else
      ng = x;
  }

  cout << ok << endl;
  return 0;
}