Submission #505096

#	Time	Username	Problem	Language	Result	Execution time	Memory
505096		HappyPacMan	Aliens (IOI16_aliens)	C++14	4 / 100	3 ms	1484 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 1e5 + 6;
const ll INF = 1e12;
ll dp[MAXN];
int opt[MAXN];
vector<pair<ll,ll> > inter;

struct Line{
    int id;
    ll m,c;
    ll f(ll x){
        return m*x+c;
    }
};
vector<Line> cht;
bool check(Line f1,Line f2,Line f3){
    return (f1.c-f3.c)*(f1.m-f2.m) > (f1.c-f2.c)*(f1.m-f3.m);
}
void ins(Line fn){
    while(cht.size() > 1 && check(cht[cht.size()-2],cht.back(),fn)){
        cht.pop_back();
    }
    cht.push_back(fn);
}
Line query(ll x){
    int l=0,r=cht.size()-1;
    while(l < r){
        int m = (l+r)/2;
        if(cht[m].f(x) <= cht[m+1].f(x)) r = m;
        else l = m+1;
    }
    return cht[l];
}

int run(ll cost){
    memset(dp,1,sizeof(dp));
    memset(opt,1,sizeof(opt));
    dp[0] = opt[0] = 0;
    ins({0,-2*inter[0].first,inter[0].first*inter[0].first});
    for(int i=0;i<inter.size();i++){
        Line q = query(inter[i].second);
        ll nx = cost+inter[i].second*inter[i].second+q.f(inter[i].second);
        if(nx < dp[i+1]){
            dp[i+1] = nx;
            opt[i+1] = q.id;
        }
        if(i+1 < inter.size()){
            if(inter[i+1].first <= inter[i].second) ins({i+1,-2*inter[i+1].first,dp[i+1]-inter[i].second*(inter[i].second-2*inter[i+1].first)});
            else ins({i+1,-2*inter[i+1].first,dp[i+1]+inter[i+1].first*inter[i+1].first});
        }
    }
    cht.clear();
    int cnt=0,idx=inter.size();
    while(idx > 0){
        idx = opt[idx];
        cnt++;
    }
    return cnt;
}

ll take_photos(int n,int m,int k,vector<int> r,vector<int> c){
    for(int i=0;i<n;i++) inter.emplace_back(1ll*min(r[i],c[i]),1ll*max(r[i],c[i])+1);
    sort(inter.begin(),inter.end());
    vector<pair<ll,ll> > temp;
    for(int i=0;i<n;i++){
        while(temp.size() > 0 && temp.back().first == inter[i].first && temp.back().second <= inter[i].second) temp.pop_back();
        if(temp.empty() || temp.back().second < inter[i].second) temp.push_back(inter[i]);
    }
    swap(temp,inter);
    k = min(k,(int)inter.size());
    ll L=0,R=INF;
    while(L < R){
        ll M = (L+R+1)/2;
        if(run(M) < k) R = M-1;
        else L = M;
    }
    run(L);
    return dp[inter.size()]-L*k;
}

Compilation message (stderr)

aliens.cpp: In function 'int run(ll)':
aliens.cpp:43:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |     for(int i=0;i<inter.size();i++){
      |                 ~^~~~~~~~~~~~~
aliens.cpp:50:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |         if(i+1 < inter.size()){
      |            ~~~~^~~~~~~~~~~~~~

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