Submission #1085251

#	Time	Username	Problem	Language	Result	Execution time	Memory
1085251		Timosh	Sequence (APIO23_sequence)	C++17	47 / 100	514 ms	35836 KiB

sequence

#include <bits/stdc++.h>
#include "sequence.h"
using namespace std;

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set; // find_by_order, order_of_key

int sequence(int n, vector<int> A)
{
  int ans = 1;
  if (*max_element(A.begin(), A.end()) <= 3)
  {
    vector<vector<int>> ind(3), pref(n + 1, vector<int>(3));
    for (int i = 0; i < n; i++)
      ind[A[i] - 1].push_back(i);
    for (int i = 0; i < n; i++)
    {
      for (int j = 0; j < 3; j++)
        pref[i + 1][j] = pref[i][j];
      pref[i + 1][A[i] - 1]++;
    }
    int l = 1, r = ind[0].size();
    while (l <= r)
    {
      int m = (l + r) / 2;
      bool f = 0;
      for (int i = 0; i + m - 1 < ind[0].size(); i++)
      {
        if (m * 2 >= ind[0][i + m - 1] - ind[0][i] + 1)
        {
          f = 1;
          ans = max(ans, m);
        }
      }
      if (f)
        l = m + 1;
      else
        r = m - 1;
    }
    /////
    l = 1, r = ind[2].size();
    while (l <= r)
    {
      int m = (l + r) / 2;
      bool f = 0;
      for (int i = 0; i + m - 1 < ind[2].size(); i++)
      {
        if (m * 2 >= ind[2][i + m - 1] - ind[2][i] + 1)
        {
          f = 1;
          ans = max(ans, m);
        }
      }
      if (f)
        l = m + 1;
      else
        r = m - 1;
    }
    /////
    l = 1, r = ind[1].size();
    while (l <= r)
    {
      int m = (l + r) / 2;
      bool f = 0;
      for (int i = 0; i + m - 1 < ind[1].size(); i++)
      {
        int a = pref[ind[1][i + m - 1] + 1][0] - pref[ind[1][i]][0];
        int b = pref[ind[1][i + m - 1] + 1][2] - pref[ind[1][i]][2];
        int len = ind[1][i + m - 1] - ind[1][i] + 1 - 2 * min(a, b);
        if (m * 2 >= len)
          ans = max(ans, m), f = 1;
      }
      if (f)
        l = m + 1;
      else
        r = m - 1;
    }
    return ans;
  }
  if (n <= 2e3)
  {
    for (int i = 0; i < n; i++)
    {
      ordered_set hm;
      for (int j = i; j < n; j++)
      {
        hm.insert(A[j]);
        int x = *hm.find_by_order((j - i) / 2);
        int y = *hm.find_by_order((j - i + 1) / 2);
        ans = max(ans, (int)hm.order_of_key(x + 1) - (int)hm.order_of_key(x));
        ans = max(ans, (int)hm.order_of_key(y + 1) - (int)hm.order_of_key(y));
      }
    }
    bool works = 1;
    int last = 0;
    for (int i = 0; i < n; i++)
    {
      if (last > A[i])
      {
        for (int j = i; j < n; j++)
        {
          if (last < A[j])
            works = 0;
          last = A[j];
        }
        break;
      }
      last = A[i];
    }
    if (!works)
      return ans;
  }
  int last = 0;
  vector<int> cnt(n + 1);
  for (int i = 0; i < n; i++)
  {
    if (last > A[i])
      break;
    cnt[A[i]]++;
    ans = max(ans, cnt[A[i]]);
    last = A[i];
  }
  last = 0;
  for (int i = 1; i <= n; i++)
    cnt[i] = 0;

  for (int i = n - 1; i >= 0; i--)
  {
    if (last > A[i])
      break;
    last = A[i];
    cnt[A[i]]++;
    ans = max(ans, cnt[A[i]]);
  }
  for (int i = 1; i <= n; i++)
    cnt[i] = 0;

  sort(A.begin(), A.end());
  for (int i = 0; i < n; i++)
    cnt[A[i]]++;
  for (int i = n / 2; i < n; i++)
    ans = max(ans, cnt[A[i]]);
  return ans;
}

Compilation message (stderr)

sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:29:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |       for (int i = 0; i + m - 1 < ind[0].size(); i++)
      |                       ~~~~~~~~~~^~~~~~~~~~~~~~~
sequence.cpp:48:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |       for (int i = 0; i + m - 1 < ind[2].size(); i++)
      |                       ~~~~~~~~~~^~~~~~~~~~~~~~~
sequence.cpp:67:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   67 |       for (int i = 0; i + m - 1 < ind[1].size(); i++)
      |                       ~~~~~~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 17 / 17
• Subtask 3: 7 / 7
• Subtask 4: 12 / 12
• Subtask 5: 0 / 13
• Subtask 6: 0 / 22
• Subtask 7: 0 / 18