Problem p03202 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define srep(i, s, t) for (int i = (int)(s); i < (int)(t); ++i)
#define each(a, b) for (auto &(a) : (b))
#define all(v) (v).begin(), (v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define cmx(x, y) x = max(x, y)
#define cmn(x, y) x = min(x, y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout << #x << " = " << (x) << endl
#define spair(p) cout << #p << ": " << p.fi << " " << p.se << endl
#define sar(a, n)                                                              \
  cout << #a << ":";                                                           \
  rep(pachico, n) cout << " " << a[pachico];                                   \
  cout << endl
#define svec(v)                                                                \
  cout << #v << ":";                                                           \
  rep(pachico, v.size()) cout << " " << v[pachico];                            \
  cout << endl
#define svecp(v)                                                               \
  cout << #v << ":";                                                           \
  each(pachico, v) cout << " {" << pachico.first << ":" << pachico.second      \
                        << "}";                                                \
  cout << endl
#define sset(s)                                                                \
  cout << #s << ":";                                                           \
  each(pachico, s) cout << " " << pachico;                                     \
  cout << endl
#define smap(m)                                                                \
  cout << #m << ":";                                                           \
  each(pachico, m) cout << " {" << pachico.first << ":" << pachico.second      \
                        << "}";                                                \
  cout << endl

using namespace std;

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 200005;

int n, a[MAX_N];

bool possible(int cri) {
  map<int, int> mp;
  int prv = 0;
  rep(i, n) {
    if (a[i] <= prv) {
      mp.erase(mp.upper_bound(a[i]), mp.end());
      rrep(j, a[i] + 1) {
        if (j == 0) {
          return false;
        }
        if (mp[j] < cri - 1) {
          mp[j]++;
          break;
        } else {
          mp.erase(j);
        }
      }
    }
    prv = a[i];
  }
  return true;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  int flag = -1;
  rep(i, n) {
    cin >> a[i];
    if (flag >= a[i]) {
      flag = INF;
    }
    cmx(flag, a[i]);
  }
  if (flag != INF) {
    cout << "1\n";
    return 0;
  }
  int l = 0, r = n;
  while (r - l > 1) {
    int mid = (l + r) / 2;
    if (possible(mid)) {
      r = mid;
    } else {
      l = mid;
    }
  }
  cout << r << "\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define srep(i, s, t) for (int i = (int)(s); i < (int)(t); ++i)
#define each(a, b) for (auto &(a) : (b))
#define all(v) (v).begin(), (v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define cmx(x, y) x = max(x, y)
#define cmn(x, y) x = min(x, y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout << #x << " = " << (x) << endl
#define spair(p) cout << #p << ": " << p.fi << " " << p.se << endl
#define sar(a, n)                                                              \
  cout << #a << ":";                                                           \
  rep(pachico, n) cout << " " << a[pachico];                                   \
  cout << endl
#define svec(v)                                                                \
  cout << #v << ":";                                                           \
  rep(pachico, v.size()) cout << " " << v[pachico];                            \
  cout << endl
#define svecp(v)                                                               \
  cout << #v << ":";                                                           \
  each(pachico, v) cout << " {" << pachico.first << ":" << pachico.second      \
                        << "}";                                                \
  cout << endl
#define sset(s)                                                                \
  cout << #s << ":";                                                           \
  each(pachico, s) cout << " " << pachico;                                     \
  cout << endl
#define smap(m)                                                                \
  cout << #m << ":";                                                           \
  each(pachico, m) cout << " {" << pachico.first << ":" << pachico.second      \
                        << "}";                                                \
  cout << endl

using namespace std;

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 200005;

int n, a[MAX_N];

bool possible(int cri) {
  map<int, int> mp;
  int prv = 0;
  rep(i, n) {
    if (a[i] <= prv) {
      mp.erase(mp.upper_bound(a[i]), mp.end());
      rrep(j, a[i] + 1) {
        if (j == 0) {
          return false;
        }
        if (mp[j] < cri - 1) {
          mp[j]++;
          break;
        } else {
          mp.erase(j);
        }
      }
    }
    prv = a[i];
  }
  return true;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  int flag = -1;
  rep(i, n) {
    cin >> a[i];
    if (flag >= a[i]) {
      flag = INF;
    }
    cmx(flag, a[i]);
  }
  if (flag != INF) {
    cout << "1\n";
    return 0;
  }
  int l = 1, r = n;
  while (r - l > 1) {
    int mid = (l + r) / 2;
    if (possible(mid)) {
      r = mid;
    } else {
      l = mid;
    }
  }
  cout << r << "\n";
  return 0;
}