Submission #899026

#	Time	Username	Problem	Language	Result	Execution time	Memory
899026		WLZ	Mobile (BOI12_mobile)	C++17	100 / 100	228 ms	104876 KiB

mobile

#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "debug.hpp"
#include "lib/geodeb.h"
#else
#define debug(...)
#define GD_INIT(...)
#define GD_POINT(...)
#define GD_LAYER(...)
#define GD_LINE(...)
#define GD_SEGMENT(...)
#endif

using ld = long double;
constexpr ld inf = numeric_limits<long double>::infinity();
constexpr ld eps = 1e-9;

// https://github.com/kth-competitive-programming/kactl/blob/main/content/geometry/Point.h
template<class T>
struct Point {
    typedef Point P;
    T x, y;
    explicit Point(T _x = 0, T _y = 0) : x(_x), y(_y) {}
    P operator+(P p) const { return P(x + p.x, y + p.y); }
    P operator-(P p) const { return P(x - p.x, y - p.y); }
    P operator/(T d) const { return P(x / d, y / d); }
    T dist2() const { return x*x + y*y; }
    ld dist() const { return sqrt((ld) dist2()); }
    P perp() const { return P(-y, x); }
};

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    GD_INIT("geodeb.html");

    int n; ld l; cin >> n >> l;
    vector< Point<int> > p1(n);
    for (int i = 0; i < n; i++) cin >> p1[i].x >> p1[i].y;
    int px = (int) -2e9, py = -2e9;
    vector< Point<ld> > p;
    for (auto &[x, y] : p1) {
        if (x == px) py = min(py, abs(y));
        else {
            if (px > (int) -2e9) p.emplace_back(px, py);
            px = x; py = abs(y);
        }
    }
    p.emplace_back(px, py);

    n = (int) p.size();
    GD_SEGMENT(0, 0, l, 0, "black bold");
    for (auto &[x, y] : p) GD_POINT(x, y, "black bold");

    vector<ld> ends = {-inf};
    vector< Point<ld> > st = {p[0]};

    for (int i = 1; i < n; i++) {
        GD_LAYER();
        GD_POINT(p[i].x, p[i].y, "red bold");

        while (true) {
            GD_LAYER();
            for (auto &e : ends) GD_POINT(clamp(e, 0.0l, l), 0, "red bold");

            auto q = st.back();
            GD_SEGMENT(p[i].x, p[i].y, q.x, q.y, "red bold");
            auto m = (p[i] + q) / 2;
            GD_POINT(m.x, m.y, "blue bold");
            auto tmp = (q - p[i]).perp() + m;
            GD_LINE(m.x, m.y, tmp.x, tmp.y, "black bold");
            ld k = -m.y / (q.x - p[i].x);
            ld x = m.x - k * (q.y - p[i].y);
            GD_POINT(x, 0, "blue bold");
            if (x < ends.back()) {
                st.pop_back(); ends.pop_back();
            } else {
                st.push_back(p[i]); ends.push_back(x);
                break;
            }
        }
        for (auto &e : ends) GD_POINT(clamp(e, 0.0l, l), 0, "red bold");
    }
    ends.push_back(inf);
    ld ans = 0.0;
    for (int i = 0; i < (int) st.size(); i++) {
        ld a = max(0.0l, ends[i]), b = min(l, ends[i + 1]);
        if (a < b) {
            ans = max(ans, (Point<ld>(a, 0) - st[i]).dist());
            ans = max(ans, (Point<ld>(b, 0) - st[i]).dist());
        }
    }
    cout << fixed << setprecision(4) << ans << '\n';

    return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:54:16: warning: unused structured binding declaration [-Wunused-variable]
   54 |     for (auto &[x, y] : p) GD_POINT(x, y, "black bold");
      |                ^~~~~~
mobile.cpp:65:24: warning: unused variable 'e' [-Wunused-variable]
   65 |             for (auto &e : ends) GD_POINT(clamp(e, 0.0l, l), 0, "red bold");
      |                        ^
mobile.cpp:71:18: warning: variable 'tmp' set but not used [-Wunused-but-set-variable]
   71 |             auto tmp = (q - p[i]).perp() + m;
      |                  ^~~
mobile.cpp:83:20: warning: unused variable 'e' [-Wunused-variable]
   83 |         for (auto &e : ends) GD_POINT(clamp(e, 0.0l, l), 0, "red bold");
      |                    ^

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
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• Subtask 21: 5 / 5