Submission #23993

#	Time	Username	Problem	Language	Result	Execution time	Memory
23993		gs14004	Aliens (IOI16_aliens)	C++11	60 / 100	2000 ms	356976 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long lint;
typedef pair<lint, lint> pi;

vector<pi> v;
vector<vector<lint>> dp;

struct cht{
    vector<pi> v;
    void clear(){ v.clear(); }
    long double cross(pi  a, pi b){
        return ((long double)(b.second - a.second) / (b.first - a.first));
    }
    void add_line(int x, lint y){
        while(v.size() >= 2 && cross(v[v.size()-2], v.back()) > cross(v.back(), pi(x, y))){
            v.pop_back();
        }
        v.push_back({x, y});
    }
    lint query(int x){
        int s = 0, e = v.size()-1;
        auto f = [&](int p){
            return v[p].first * x + v[p].second;
        };
        while(s != e){
            int m = (s+e)/2;
            if(f(m) <= f(m+1)) e = m;
            else s = m+1;
        }
        return f(s);
    }
}cht;

long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
    vector<pi> w;
    for(int i=0; i<n; i++){
        if(r[i] > c[i]) swap(r[i], c[i]);
        w.push_back({r[i]-1, c[i]});
    }
    sort(w.begin(), w.end(), [&](const pi &a, const pi &b){
        return pi(a.first, -a.second) < pi(b.first, -b.second);
    });
    for(auto &i : w){
        if(v.empty() || v.back().second < i.second){
            v.push_back(i);
        }
    }
    dp.resize(k+1);
    for(auto &i : dp) i.resize(v.size() + 1);
    dp[0][0] = 0;
    for(int i=1; i<=v.size(); i++){
        dp[0][i] = 1e18;
    }
    for(int i=1; i<=k; i++){
        cht.clear();
        for(int j=1; j<=v.size(); j++){
            cht.add_line(2 * v[j-1].first, dp[i-1][j-1] + 1ll * v[j-1].first * v[j-1].first);
            dp[i][j] = cht.query(-v[j-1].second) + 1ll * v[j-1].second * v[j-1].second;
            if(j != v.size()){
                lint cost = max(0ll, v[j-1].second - v[j].first);
                dp[i][j] -= cost * cost;
            }
        }
    }
    return dp[k][v.size()];
}

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:53:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=1; i<=v.size(); i++){
                   ^
aliens.cpp:58:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=1; j<=v.size(); j++){
                       ^
aliens.cpp:61:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(j != v.size()){
                  ^

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