Submission #638288

#	Time	Username	Problem	Language	Result	Execution time	Memory
638288		ggoh	Aliens (IOI16_aliens)	C++14	4 / 100	1 ms	212 KiB

aliens

#include "aliens.h"
#include<bits/stdc++.h>
using namespace std;
#define sz(v) ((int)(v).size())
typedef long long lint;
typedef pair<int,int> pii;

vector<pii>Vtmp,V;
lint sq(int L)
{
  return 1ll*L*L;
}
int a[100004],b[100004];
struct Line{
  lint a,b;
  int k;
};
int piv,knum;
vector<Line>CHT;
lint D;
bool check1(Line A,Line B,Line C)
{
  if((long double)(B.b-A.b)/(A.a-B.a) > (long double)(C.b-B.b)/(B.a-C.a))return 1;
  else return 0;
}
bool check2(Line A,Line B,lint x)
{
  if((B.b-A.b) < x*(A.a-B.a)) return 1;
  else return 0;
}

void insert_line(Line L)
{
  while((int)CHT.size()>2 && check1(CHT[sz(CHT)-2],CHT[sz(CHT)-1],L))CHT.pop_back();
  CHT.push_back(L);
  piv=min(piv,sz(CHT)-1);
}
lint gets(lint x)
{
  while(piv+1<sz(CHT) && check2(CHT[piv],CHT[piv+1],x))piv++;
  knum=CHT[piv].k+1;
  return CHT[piv].a * x + CHT[piv].b;
}
lint take_photos(int n, int m, int K, std::vector<int> r, std::vector<int> c) {
  for(int i=0;i<n;i++)
  {
    if(r[i]<c[i])swap(r[i],c[i]);
    Vtmp.push_back({r[i],-c[i]});
  }
  sort(Vtmp.begin(),Vtmp.end());
  int mini=1e9;
  for(int i=sz(Vtmp)-1;i>=0;i--)
  {
    if(mini>-Vtmp[i].second)V.push_back({Vtmp[i].first,-Vtmp[i].second});
    mini=min(mini,-Vtmp[i].second);
  }
  sort(V.begin(),V.end());
  n=sz(V);
  for(int i=1;i<=n;i++)
  {
    a[i]=V[i-1].second;
    b[i]=V[i-1].first+1;
  }
  K=min(K,n);
  lint p=0,q=1ll*m*m,h;
  while(p!=q-1)
  {
    h=(p+q)/2;
    CHT.clear();
    insert_line({-4*a[1],2*sq(a[1]),0});
    piv=0;
    for(int i=1;i<=n;i++)
    {
        D=gets(b[i])+2*sq(b[i])+(2*h+1);
        insert_line({-4*a[i+1],D+2*(sq(a[i+1])-sq(b[i]-min(a[i+1],b[i]))),knum});
    }
    if(knum>=K)p=h;
    else q=h;
  }
  int le,ri;
  lint Dl,Dr;
  CHT.clear();
  insert_line({-4*a[1],2*sq(a[1]),0});
  piv=0;
  for(int i=1;i<=n;i++)
  {
    D=gets(b[i])+2*sq(b[i])+(2*p+1);
    insert_line({-4*a[i+1],D+2*(sq(a[i+1])-sq(b[i]-min(a[i+1],b[i]))),knum});
  }
  ri=knum;Dr=(D-(2*p+1)*knum)/2;

  if(K==ri)return Dr;
  else return Dr+(p+1)*(ri-K);
}

Compilation message (stderr)

aliens.cpp: In function 'lint take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:80:7: warning: unused variable 'le' [-Wunused-variable]
   80 |   int le,ri;
      |       ^~
aliens.cpp:81:8: warning: unused variable 'Dl' [-Wunused-variable]
   81 |   lint Dl,Dr;
      |        ^~

• Subtask 1: 4 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40