Submission #172839

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
172839	2020-01-02T16:38:00 Z	RafaelSus	Split the sequence (APIO14_sequence)	C++14	0 / 100	98 ms	83848 KB

sequence

#include <bits/stdc++.h>
 
using namespace std;
const int N = 2e5 + 5;
typedef long long ll;
const ll inf=1e15;
#define pb push_back
const int INF=(0x3f3f3f3f);
 
vector<ll>m,b;
vector<int>idx;
int ptr;
 
bool bad(int f1,int f2,ll _m,ll _b)
{
  int f3=f2;
  f2--;
  f1--;
  m.pb(_m);
  b.pb(_b);
	bool ok=(b[f3]-b[f1])*(m[f1]-m[f2])>=(b[f2]-b[f1])*(m[f1]-m[f3]);
	m.pop_back();
	b.pop_back();
	return ok;
} 
 
void add(ll _m,ll _b,int _idx){
  while(m.size()>=2/*&&((b.back()-_b)*(_m-m[m.size()-2])>=(b[b.size()-2]-_b)*(_m-m.back()))*/){
    if(bad(m.size()-2,m.size()-1,_m,_b)){
      m.pop_back();
      b.pop_back();
      idx.pop_back();
    }else break;
  }
  m.pb(_m);
  b.pb(_b);
  idx.pb(_idx);
}
 
ll func(int pos,ll x){
  return m[pos]*x+b[pos];
}
 
pair<ll,int>get(ll x){
  if(ptr>=m.size())ptr=m.size()-1;
  while(ptr+1<m.size()&&func(ptr,x)<=func(ptr+1,x))ptr++;
  return {func(ptr,x),idx[ptr]};
}
int path[N][205];
void print(int st,int k){
  if(path[st][k]==0){
    cout<<st<<' ';
    return;
  }
  print(path[st][k],k-1);
  cout<<st<<' ';
}
ll dp[2][N];
 
int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);cout.tie(0);
  
  int n,k;
  cin>>n>>k;
  ll a[n+1],pref[n+1]={};
  for(int i=1;i<=n;i++){
    cin>>a[i];
    pref[i]=pref[i-1]+a[i];
  }
  
  for(int i=1;i<=n;i++){
    dp[1][i]=pref[i]*(pref[n]-pref[i]);
    path[i][1]=0;
  }
  for(int i=2;i<=k;i++){
    int v=(i-1)%2;
    m.clear();
    b.clear();
    idx.clear();
    ptr=0;
    add(0,0,0);
    for(int j=i-1;j<=n;j++){
      if(j<i){
        if(j==i-1){
          add(-pref[j],dp[v][j],j);
        }
        continue;
      }
      pair<ll,int>tmp=get(pref[n]-pref[j]);
      dp[v^1][j]=tmp.first+(pref[n]-pref[j])*pref[j];
      path[j][i]=tmp.second;
      add(-pref[j],dp[v][j],j);
    }
  }
  ll mx=0,st=1;
  for(int i=1;i<=n;i++){
    if(dp[k%2][i]>mx){
      mx=dp[k%2][i];
      st=i;
    }
  }
  cout<<mx<<'\n';
  print(st,k);
}

Compilation message

sequence.cpp: In function 'std::pair<long long int, int> get(ll)':
sequence.cpp:45:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(ptr>=m.size())ptr=m.size()-1;
      ~~~^~~~~~~~~~
sequence.cpp:46:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(ptr+1<m.size()&&func(ptr,x)<=func(ptr+1,x))ptr++;
         ~~~~~^~~~~~~~~

Subtask #1
0 / 11.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	2 ms	376 KB	contestant didn't find the optimal answer: 107 < 108
2	Halted	0 ms	0 KB	-

Subtask #2
0 / 11.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	2 ms	376 KB	contestant didn't find the optimal answer: 1090726 < 1093956
2	Halted	0 ms	0 KB	-

Subtask #3
0 / 11.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	2 ms	504 KB	contestant found the optimal answer: 610590000 == 610590000
2	Correct	2 ms	504 KB	contestant found the optimal answer: 311760000 == 311760000
3	Correct	3 ms	504 KB	contestant found the optimal answer: 1989216017013 == 1989216017013
4	Incorrect	2 ms	504 KB	contestant didn't find the optimal answer: 1019415406153 < 1499437552673
5	Halted	0 ms	0 KB	-