Problem p03202 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define mp make_pair
#define PI pair<int, int>
#define poly vector<ll>
#define For(i, l, r) for (int i = (int)(l); i <= (int)(r); i++)
#define Rep(i, r, l) for (int i = (int)(r); i >= (int)(l); i--)
#define pb push_back
#define fi first
#define se second
inline char gc() {
  static char buf[100000], *p1 = buf, *p2 = buf;
  return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2)
             ? EOF
             : *p1++;
}
#define gc getchar
inline ll read() {
  ll x = 0;
  char ch = gc();
  bool positive = 1;
  for (; !isdigit(ch); ch = gc())
    if (ch == '-')
      positive = 0;
  for (; isdigit(ch); ch = gc())
    x = x * 10 + ch - '0';
  return positive ? x : -x;
}
inline void write(ll a) {
  if (a < 0) {
    a = -a;
    putchar('-');
  }
  if (a >= 10)
    write(a / 10);
  putchar('0' + a % 10);
}
inline void writeln(ll a) {
  write(a);
  puts("");
}
inline void wri(ll a) {
  write(a);
  putchar(' ');
}
inline ull rnd() { return ((ull)rand() << 30 ^ rand()) << 4 | rand() % 4; }
const int N = 200005;
int n, a[N];
bool check(int x) {
  map<int, int> M;
  For(i, 2, n) {
    if (a[i] <= a[i - 1]) {
      M[a[i]]++;
      while (1) {
        auto it = M.end();
        it--;
        if (it->fi > a[i])
          M.erase(it);
        else
          break;
      }
      int len = a[i]; // cout<<len<<" "<<M[len]<<endl;
      while (M[len] == x) {
        if (len == 1)
          return 0;
        M.erase(len);
        M[--len]++;
      }
    }
  }
  return 1;
}
int main() {
  n = read();
  For(i, 1, n) a[i] = read();
  // cout<<check(2)<<endl; return 0;
  int l = 1, r = n;
  while (l < r) {
    int mid = (l + r) >> 1;
    if (check(mid))
      r = mid;
    else
      l = mid + 1;
    // cout<<l<<" "<<r<<endl;
  }
  cout << l << endl;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define mp make_pair
#define PI pair<int, int>
#define poly vector<ll>
#define For(i, l, r) for (int i = (int)(l); i <= (int)(r); i++)
#define Rep(i, r, l) for (int i = (int)(r); i >= (int)(l); i--)
#define pb push_back
#define fi first
#define se second
inline char gc() {
  static char buf[100000], *p1 = buf, *p2 = buf;
  return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2)
             ? EOF
             : *p1++;
}
#define gc getchar
inline ll read() {
  ll x = 0;
  char ch = gc();
  bool positive = 1;
  for (; !isdigit(ch); ch = gc())
    if (ch == '-')
      positive = 0;
  for (; isdigit(ch); ch = gc())
    x = x * 10 + ch - '0';
  return positive ? x : -x;
}
inline void write(ll a) {
  if (a < 0) {
    a = -a;
    putchar('-');
  }
  if (a >= 10)
    write(a / 10);
  putchar('0' + a % 10);
}
inline void writeln(ll a) {
  write(a);
  puts("");
}
inline void wri(ll a) {
  write(a);
  putchar(' ');
}
inline ull rnd() { return ((ull)rand() << 30 ^ rand()) << 4 | rand() % 4; }
const int N = 200005;
int n, a[N];
bool check(int x) {
  map<int, int> M;
  For(i, 2, n) {
    if (a[i] <= a[i - 1]) {
      M[a[i]]++;
      while (1) {
        auto it = M.end();
        it--;
        if (it->fi > a[i])
          M.erase(it);
        else
          break;
      }
      int len = a[i]; // cout<<len<<" "<<M[len]<<endl;
      while (M[len] == x) {
        if (len == 1 || x == 1)
          return 0;
        M.erase(len);
        M[--len]++;
      }
    }
  }
  return 1;
}
int main() {
  n = read();
  For(i, 1, n) a[i] = read();
  // cout<<check(2)<<endl; return 0;
  int l = 1, r = n;
  while (l < r) {
    int mid = (l + r) >> 1;
    if (check(mid))
      r = mid;
    else
      l = mid + 1;
    // cout<<l<<" "<<r<<endl;
  }
  cout << l << endl;
}