Submission #985202

#	Time	Username	Problem	Language	Result	Execution time	Memory
985202		Faisal_Saqib	Sequence (APIO23_sequence)	C++17	0 / 100	2075 ms	111972 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>



using namespace std;


const int LIM=2e3+10;
vector<vector<int>> pre;
int ans=1;
const int MN=5e5+10;
int mx_e=4;
int a[MN];
int n;
map<int,vector<int>> ind;
void compute_pre()
{
  // LIM x LIM
  pre.assign(LIM,vector<int>(LIM));
  for(int i=1;i<=n;i++)
    pre[0][i]=0;
  for(int i=1;i<=n;i++)
  {
    for(int j=1;j<=n;j++)
    {
      pre[i][j]=pre[i-1][j]+(a[i-1]<=j);
    }
  }
}
void adv_pre()
{
  // MN x 4
  pre.assign(MN,vector<int>(6));
  for(int i=1;i<=3;i++)
    pre[0][i]=0;
  for(int i=1;i<=n;i++)
  {
    for(int j=1;j<=3;j++)
    {
      pre[i][j]=pre[i-1][j]+(a[i-1]<=j);
    }
  }
}
int count_less(int l,int r,int x)
{
  return pre[r+1][x]-pre[l][x];
}
// int count(int l,int r,int x)
// {
//   int tp=count_less(l,r,x)-count_less(l,r,x-1);
//   return tp;
// }
int count(int l,int r,int x)
{
  auto it=lower_bound(begin(ind[x]),end(ind[x]),l);
  auto it1=upper_bound(begin(ind[x]),end(ind[x]),r);
  return it1-it;
}
int solve_(int l,int r)
{
  int s=0;
  int e=mx_e;
  int len=(r-l+1);
  int flooor=(len-1)/2;
  /*
  if len is even
    then there are two medain = floor((len-1)/2) and ceil((len-1)/2)
  else if len is odd        
    single medain
  */
  while(s+1<e)
  {
    int mid=(s+e)/2;
    if(count_less(l,r,mid)<=flooor)
    {
      s=mid;
    }
    else{
      e=mid;
    }
  }
  ans=max(ans,count(l,r,e));
  if(len%2==0)
  {
    int ceill=flooor+1;
    s=0;
    e=mx_e;
    while(s+1<e)
    {
      int mid=(s+e)/2;
      if(count_less(l,r,mid)<=ceill)
      {
        s=mid;
      }
      else{
        e=mid;
      }
    }
    ans=max(ans,count(l,r,e));
  }
  return 0;
}
int sequence(int NP, std::vector<int> AP) {
  n=NP;
  for(int i=0;i<n;i++)
    a[i]=AP[i];
  // if(NP<LIM)
  // {
  //   compute_pre();
  //   mx_e=n+1;
  //   int ans=1;
  //   for(int l=0;l<n;l++)
  //   {
  //     for(int r=l+1;r<n;r++)
  //     {
  //       ans=max(ans,solve_(l,r));
  //     }
  //   }
  //   return ans;
  //   // cout<<ans<<endl;
  // }
  // else{
    adv_pre();
    for(int i=0;i<n;i++)
      ind[a[i]].push_back(i);
    set<int> asp;
    for(int i=0;i<n;i++)
      asp.insert(a[i]);
    for(auto x:asp)
    {
      for(int i=0;i<ind[x].size();i++)
      {
        for(int j=(i+1);j<ind[x].size();j++)
        {
          ans=max(ans,solve_(ind[x][i],ind[x][j]));
        }
      }
    }
    return ans;
  // }
  return 0;
}

Compilation message (stderr)

sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:132:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  132 |       for(int i=0;i<ind[x].size();i++)
      |                   ~^~~~~~~~~~~~~~
sequence.cpp:134:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  134 |         for(int j=(i+1);j<ind[x].size();j++)
      |                         ~^~~~~~~~~~~~~~

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