Submission #224932

#	Time	Username	Problem	Language	Result	Execution time	Memory
224932		jhnah917	Aliens (IOI16_aliens)	C++14	4 / 100	6 ms	384 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>
#define x first
#define y second
#define all(v) v.begin(), v.end()
using namespace std;
 
typedef long long ll;
typedef pair<ll, ll> p;
 
int n, m, k;
ll dp[101010];
int cut[101010];
p a[101010];
vector<p> v;
 
struct CHT{
    struct Line{
        ll a, b, c;
        Line(){ a = b = c = 0; }
        Line(ll a, ll b, ll c) : a(a), b(b), c(c) {}
        ll f(ll x){ return a*x+b; }
    };
    vector<Line> v; int pv;
    void init(){ v.clear(); pv = 0; }
    int chk(const Line &a, const Line &b, const Line &c){
        return (a.b - b.b) * (c.a - b.a) >= (b.b - c.b) * (b.a - a.a);
    }
    void update(Line l){
        if(v.size() && v.back().a == l.a){ v.back() = l; return; }
        while(v.size() >= 2 && chk(v[v.size()-2], v.back(), l)) v.pop_back();
        v.push_back(l);
        if(pv >= v.size()) pv = v.size() - 1;
    }
    p query(ll x){
        while(pv+1 < v.size() && v[pv].f(x) >= v[pv+1].f(x)) pv++;
        return {v[pv].f(x), v[pv].c};
    }
} cht;
 
void init(int N, int M, int K, const vector<int> &R, const vector<int> &C){
    m = M, k = K; v.clear();
    for(int i=0; i<N; i++) v.emplace_back(max(R[i], C[i]) + 1, min(R[i], C[i]));
    sort(all(v));
    for(int i=0; i<N; i++){
        while(n && a[n].y >= v[i].y) n--;
        a[++n] = v[i];
    }
}

int chk(ll c){
    cht.init(); cht.update(CHT::Line(-2 * a[1].y, a[1].y * a[1].y, 0));
    for(int i=1; i<=n; i++){
        auto t = cht.query(a[i].x);
        dp[i] = t.x + a[i].x * a[i].x + c;
        cut[i] = cut[t.y] + 1;
        ll ta = a[i+1].y, tb = max(0LL, a[i].x - a[i+1].y);
        ll aa = -2 * a[i+1].y;
        ll bb = dp[i] + ta*ta - tb*tb;
        cht.update(CHT::Line(aa, bb, i));
    }
    return cut[n];
}
 
ll take_photos(int N, int M, int K, vector<int> R, vector<int> C){
    init(N, M, K, R, C);
    int q = min(n, k);
 
    ll l = 0, r = 1e15;
    while(l < r){
        ll m = l + r >> 1;
        if(chk(m) <= q) r = m;
        else l = m + 1;
    }
    chk(r);
    return dp[n] - r * q;
}
 
// g++ -O2 -std=c++11 -static -o main grader.cpp aliens.cpp aliens.h

Compilation message (stderr)

aliens.cpp: In member function 'void CHT::update(CHT::Line)':
aliens.cpp:33:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(pv >= v.size()) pv = v.size() - 1;
            ~~~^~~~~~~~~~~
aliens.cpp: In member function 'p CHT::query(ll)':
aliens.cpp:36:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while(pv+1 < v.size() && v[pv].f(x) >= v[pv+1].f(x)) pv++;
               ~~~~~^~~~~~~~~~
aliens.cpp: In function 'll take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:71:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
         ll m = l + r >> 1;
                ~~^~~

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