Submission #985185

#	Time	Username	Problem	Language	Result	Execution time	Memory
985185		Faisal_Saqib	Sequence (APIO23_sequence)	C++17	28 / 100	2019 ms	94016 KiB

sequence

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

// #include "grader.cpp"

using namespace std;


const int LIM=2e3+10;
int pre[LIM][LIM];
const int MN=5e5+10;
int a[MN],l_[MN],r_[MN],eq_[MN];
int n;
map<int,vector<int>> ind;
void compute_pre()
{
  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);
    }
  }
}
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);
  // if(tp==4)
  //   cout<<"FOR "<<l<<' '<<r<<' '<<x<<endl;
  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 x)
{
  int cntp=count_(l,r,x);
  int len=(r-l+1);
  int cnt_p=len/2;
  if(cntp>=cnt_p)
  {
    return cntp;
  }
  else{
    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();
    int ans=1;
    for(int l=0;l<n;l++)
    {
      for(int r=l+1;r<n;r++)
      {
        int s=0;
        int e=n+1;
        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=n+1;
          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 ans;
    // cout<<ans<<endl;
  }
  else{
    for(int i=0;i<=n;i++)
      l_[i]=r_[i]=-1;
    for(int i=0;i<n;i++)
    {
      if(l_[a[i]]==-1)
        l_[a[i]]=i;
      r_[a[i]]=i;
    }
    int ans=1;
    for(int i=0;i<n;i++)
      ind[a[i]].push_back(i);
    for(int i=0;i<n;i++)
      ans=max(ans,solve_(l_[a[i]],r_[a[i]],a[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],x));
        }
      }
    }
    return ans;
  }
  return 0;
}

Compilation message (stderr)

sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:135:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  135 |       for(int i=0;i<ind[x].size();i++)
      |                   ~^~~~~~~~~~~~~~
sequence.cpp:137:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  137 |         for(int j=(i+1);j<ind[x].size();j++)
      |                         ~^~~~~~~~~~~~~~

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