제출 #684206

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
684206		Brownbear2710	Mobile (BOI12_mobile)	C++14	0 / 100	1096 ms	81152 KiB

mobile

/*
    So, which of the favours
    of your Lord would you deny?
*/

#include <bits/stdc++.h>

#ifdef ADIB_PC
#include "dbg.h"
#else
#define dbg(...)
#endif

using namespace std;
using ll = long long;
using ld = long double;

#define fast_IO ios_base::sync_with_stdio(0), cin.tie(NULL);
#define show(x) cout << #x << ": " << x << endl;
#define all(x) x.begin(), x.end()
#define MAXN 200005

struct point
{
    ld x, y;
    point(){}
    point(ld _x, ld _y) : x(_x), y(_y) {}
    bool operator<(point &p) const
    {
        if(x != p.x) x < p.x;
        return y < p.y;
    }
};

vector<point> pts;
ld l;

bool can_cover(ld d)
{
    vector<pair<ld,ld>> seg;
    for(int i = 0; i < pts.size(); i++)
    {
        auto [x, y] = pts[i];
        if(d < y) continue;
        ld dx = sqrt(d*d-y*y);
        ld left = max((ld)0, x - dx), right = min(x + dx, l);
        seg.emplace_back(left, right);
    }
    
    double lf = 0;
    for(int i = 0; i < seg.size(); i++)
    {
        if(seg[i].first > l or seg[i].second < 0) continue;
        if(seg[i].first <= lf) lf = seg[i].second;
    }
    return lf >= l;
}

int main()
{
    fast_IO;
    int T = 1;
    // cin >> T;
    while(T--)
    {
        int n;
        cin >> n >> l;
        for(int i = 0 ; i < n; i++)
        {
            point p;
            cin >> p.x >> p.y;
            p.x = abs(p.x), p.y = abs(p.y);
            if(pts.size() == 0 || pts.back().x != p.x)
                pts.push_back(p);
        }
        ld ans = 1e15, lo  = 0, hi = 2e9;
        while(abs(lo-hi) > 0.0001)
        {
            ld mid = (lo + hi)/2;
            if(can_cover(mid))
            {
                ans = mid;
                hi = mid;
            }
            else lo = mid;
        }
        cout << fixed << setprecision(6) << ans << "\n";
    }
    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

mobile.cpp: In member function 'bool point::operator<(point&) const':
mobile.cpp:30:24: warning: statement has no effect [-Wunused-value]
   30 |         if(x != p.x) x < p.x;
      |                      ~~^~~~~
mobile.cpp: In function 'bool can_cover(ld)':
mobile.cpp:41:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<point>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |     for(int i = 0; i < pts.size(); i++)
      |                    ~~^~~~~~~~~~~~
mobile.cpp:43:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   43 |         auto [x, y] = pts[i];
      |              ^
mobile.cpp:51:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long double, long double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |     for(int i = 0; i < seg.size(); i++)
      |                    ~~^~~~~~~~~~~~

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